well you all missed the boat, the Marantz DP870U is the one to get, this unit is straight forward, analog volume control, decodes ac3 and pcm, full bass management and level controls, has 6 channel by pass, hook this baby up straight to the amps don't use a 6 channel input, it sounds excellent. as for THX/dpl, give me straight DPL, thx is a joke, it colors the sound, as for thx/dpl being better than AC3, get real.

Sorry all you guys are wrong about the Marantz AV-550. Only Duke from Yonkers NY comes close. A Sony TAE-2000ESD with Marantz DP870 will take on all comersicluding the much vaunted Yamahaha DSP-A1, which is still handicapped by inferior on-board amps and useless DSP toys. Can't wait for the upcoming Sony TAE-9000ESD!

I just bought this unit for 2 weeks. The build quality is lower from what I expected from a $1000 pre amp. However, the feature and the sound quality imade me forget about it. The remote is like a new toy to me living room. I spent whole night to learn how to use it. Actually I was going to buy the SR780 but I changed my mind to go with seperate unit when considered the lower price of AV550. I don't know how good is the sound quality of SR780 but i think the separate would give me better sound than a reciever. I use 2 ACURUS amps (A150+A100x3) for driving my NHT 2.5i, AC-1 and 1.5i speaker system. I really enjoy the sound of this system. The AV550 performed very well for a control center and for a AC-3 processor. Somehow, when I listened to music, I was not quite satisfy with AV550. So I tried by tweak it a little bit by putting the Musical Fidelity X-10D class A analog output between the AV550 and the Acurus for the 2 main channels. WOW! It's a new ball game. The sound is really improved. the AV550 transformed to be a good tube pre amp. Now I can enjoy both music listening and watching movie. I really recomend you to try that if you use AV550.
After I've been using it for 2 weeks (4-5 Hrs a day), I still not see any defect or anything I don't like about this unit. In fact I like it more and more. Considering for it discounted price that I purchased. I'm sure this unit deserve a 5 star from me.

I can only second all the good things said about this pre-amp, and for that matter all the "it needs this or that", especially stereo sub outs. I can comment on the pre-amps perceived lack of musicality due to a conversation with Marantz tech support. I originally was working on a room resonance problem and was verifying internal crossover points and basic bass management for the 550. I was told that all signals go through the DSP's in the unit. When a CD player is hooked up to the RCA connectors it forces the signal too go through 1 ADC and 2 DAC conversions before it hits the amp. That is a lot of signal processing and opportunity for loss or corruption. A example is how well AC-3 on this unit sounds, even though its a compressed signal, it has to go through only the last Digital to Analog (DAC) conversion. With this being said a CD player with a Digital out is a must if you want good performance with stereo CDs. The 550 has excellent Signal processing if kept in the digital domain and a Re-Clocker like Thetas TimeLink device or MSB's Digital Director (look guy's more inputs!) will reduce jitter to the point where you could compare the 550 to a dedicated Theta DAC. Try it you will like it.

I think you guys have it all wrong. The 550 is just totally different thanthe 600. I can see where someone would be put off by the different front
end setup. But it does more than the 600. And to my ears, it does sound
better. Different, but better. Maybe not as rolled off in the highs but
certainly better for movies and at least as good for music. In my view it
is a higher end piece of gear. The 600 was a nice piece, but the 550 is
simply a different unit, more flexible, does AC-3 and SOUNDS BETTER. Coupled
with 5 MA-500's (or MA-700's) this is a serious home theator setup at what
has to be considered a budget price. You have to spend quite a few more
dollars to get any noticably better performance.

I sold my older AV600 for this new 550 unit. I have no complaints about the 550 but it is not what the 600 was. Both are great for what they do. Kinda like a BMW and a Landrover. Each have their strengths and weaknesses when compared together so in no way do I mean to favor one over the other for any reason but my personal use. The 600 had a superior sense of sound and imaging. The 550 has a more powerfull punch to home theater and with ac3 as well as supporting more currents pieces of gear like DVD. I give both of them a 5 star rating but I sometimes wonder if I should have kept my BMW instead of trading it in on the LandRover...

550 VS. 600THX...???
The 550 undoubtably deserves the 5 star rating in every sense but here is a question. the A/V 600 has superior design features, sounds better, has THX, stereo outputs for sub and center, data cable connections and better case designs. So why buy the 550 when you have the 600 to choose instead??

I own an AV600 and agree that it's one great piece of kit -- I actually bought it after EXTENSIVE auditions of competing units, many costing 2-3 x more. Unfortunately it had no AC-3 and that's why the AV 550 really caught my attention. Unfortunately despite the AC-3 it somehow sounded sonically inferior to the AV 600, but others may view it differently.I've since returned the AV 550 and am waiting for an outboard AC3/ DTS processor from Marantz. btw, does anyone know how to connect available outboard processors using the DB15 output?
3 stars to the AV550, 5 stars to the AV600.

I bought the AV-600, which is a better unit (than the 550). DD is not a priority for me right now and I am not certain that the processing standards are set in stone. If need be, I will go outboard for DD processing. The fact that the 600 uses analogue output stages assures smoother sound. Indeed, no shrillness or other artificial effects in the treble, just natural sound. The 600 is great at uncovering added detail even with cable tv sound.
My only caveat is the amount of heat this unit generates. I will have to put a fan in the back of my equipment cabinet to aid long term preservation.

Bottom line, at current closeout prices, the AV-600 is a bargin. The 550 is no different than it's direct competition and does not stand out.

I bought the AV-550 as my introduction to DD Surround. It served me just fine until I decided to get some "real" speakers (previously was using the Carver 5.1 system but with the Energy 12XL subwoofer and HATED listening to music with them). When I put in my new NHT 3.3s, I discovered that it was just painful to listen to this as a music preamp. Since my real passion is music, this just wouldn't do. If you want a mid-fi surround processor, this is a wonderful product (GREAT ergonomics, esp with the remote). If you want music in an audiophile system, seek another product. I ended up replacing this with the Lexicon DC-1; MUCH better sound, but I'm a few thousand $$ poorer. BTW, I added a Musical Fidelity X-10D between the pre and the amp which helped significantly (but not as much as the Lexicon). I'm not 100% happy with the Lexicon performance on music either, so I'm now considering augmenting the systems with a dedicated music pre.
Associated Equipment
--------------------
Acurus A250 amplifier (front channels)
NHT SA-3 Subwoofer amps (for biamping)
Carver AV-705x amplifier (for surrounds/center)
NHT 3.3 speakers
Carver 5.1 speakers
Energy 12XL subwoofer
Panasonic A-110 DVD
Pioneer Elite PRO-1009W RPTV
Tributaries interconnects
DH Labls Silver Sonics Speaker cable
Monster Cable MCX-2S speaker cable
Lexicon DC-1 processor (replaced the Marantz)