I purchased the Onkyo M504 along with the Onkyo P304 preamp in May to replace my receiver. The difference that this pair made in my system was incredible. The most dramatic change was the depth of the soundstage and the clarity of individual instruments. The bass is very tight and controlled along with warm highs. I am using Tara Labs Prism Bi-Wire speaker cable and Tara Labs Prism 22 interconnects. These cables are a perfect match to the Onkyo components.
In addition the M504 and P304 are quality pieces. The craftsmanship is excellent. The controls and switches have a precision feel.

I am quite pleased with the pair and would recommend them to anyone.

This is a great amp. It looks like Onkyo might be phasing them out, because you can get them for $500 at J&R-- about half of their original retail (they aren't listed in the current catalog, only on-line). I couldn't be happier with mine. Clear sound, plenty of power. They seem to go very well with Vandersteen Signatures. It's entirely subjective, of course, but I'm very pleased. Bonus points: solidly built and very heavy (50 pounds). They look cool, too, with back-lit dual meters. Demerits: Plastic binding post knobs that do not allow decent spade connectors... you pretty much have to bare-wire the connection, as an earlier poster noted.
No remote control, which is fine by me-- who wants to pay for an unnecessary accessory? People who need a remote for their stereos need to listen to better music!

I bought the M-504 back in 1989 with my Onkyo Integra DX-5500 RI Compact Disc Player, Onkyo Integra TA-2600 RI Stereo Cassette Tape Deck,and Onkyo Integra P-304 Stereo PreAmplifier, and I am surprise they still the M-504 and p-304. These are excellents components, especially with the powerful 165 watt amp. I just recently bought another M-504, to upgrade my system for home theater sound. All I have to say is that the m-504 and p-304 are a classic.

In regards to a previous review, I checked and the local Circuit City did have one M504 left and they sold it to me for less than half the normal retail price.
I have been using an M504 several years now and let me say this is one sweet amp. Compared to my last amp, an Adcom, the M504 is very neutral in the midrange, a nice warm sounding treble(like my parent's old McIntosh tube amp) and an authoritative bass that's tight and there. I have my original M504 hooked up to my old Klipschhorns. I'm excited about looking into setting up a surround sound system now.

The sales rep said Onkyo isn't shipping them anymore so I feel lucky to have picked one up at a bargain.

Without reserve, I'd recommend the M504 to anyone looking for a solid amplifier with that "tube" sound without the "tube" price.

It operates like a tube power amp sound. Well, mid and high range sounds goodbut the bass feels boomy!!!!!!!

Hello,
I recently purchased this unit at Circuit City (a local store)
for $349. I think it's a great bargain. I tried hooking it
up w/ my Denon 3200 receiver. It sounded pretty nice...but
not as warmth sounding as my Denon receiver itself. I am
using NHT VS2a w/ this amp. The Onkyo sounded a bit too
bright...perhaps it's because of the NHT being sharp nature.
I am considering buying a new preamp. for the Onkyo...mainly
for music. Considering the FT Audio LW-1.

But I think the Onkyo is a good bargain if you get it around my price.
I cannot fully evaluate for you right now...but I'm not completely
satisfied because it sounded not too much better than my Denon
amplifier.

Tom

I bought my first M504 over 10 years ago and have been most impressed with it. I have recently purchased 3 more M504's to include them into my Home Theater system which includes 4 Definitive Tech. BP30 speakers along with the C/L/R 2000 center channel, a Velodyne FSR18 subwoofer, a Yamaha 992 receiver for my preamp,(which has outstanding Dolby Digital decoding), a Pioneer DVL-909 DVD-Laserdisk combo player, Onkyo CD changer and cassette deck, a Mitsubishi 40707 40" direct-view TV, 2 S-VHS VCR's, AKG headphones, Technics turntable, etc.The M504's are being discontinued??? and I was able to pick up 3 new ones from Circuit City for an unbelievable $429.97 each!!! True, J&R still has them at $549.00 each but try your local Circuit City to find a GREAT deal on an AWESOME 2 channel power amplifier!!!

I would put these amps up against the likes of Krell and McIntosh while I think they blow away Adcom, B&K, Sunfire, Parasound and ATI.

AWSOME AWSOME ALOT OF POWER. SOUNDS BETTER THAN MOST AMPS THAT COST DOUBLE THE PRICE..

I can't believe some of the good reports this amp gets. I used to sell them and admittedly you get a lot of power for your money, however the sound quality really lets it down. Have a listen to a Rotel 100w (RB870bx or newer) and you'll know what a decent power amp can sound like. If you like Japanese amps & have more money then go listen to a Luxman M-03 & you will be blown away, or try the Denon monoblocks POA-4400 & 6600s. If you want a more "dynamic" sound try a Hafler, & if you want both dynamics & smoothness go for an Aragon 4004.How someone can compare this amp to a Krell is beyond me, unless you are purely talking about $$ value, then again is a Ferrari 20 times better than your average car?...hmmm...
I give this amp 1 star for the power meters, 1 for the wattage/dollar value, 1 for the name.

This is the finest amp in the Integra lineup currently available as a new product. It is an awesome powerhouse, and it is very clean power. This amp handles the most difficult loads with aplomb, but it has one strange quirk: it takes only bare wire connections at the speaker out posts. I find myself not bothered by this, although it was a surprise. Some people think the sound is laid back or veiled, but I am driving Near 15M and 10M speakers simultaneously. Believe me whe I tell you the sound rivals the best electrostatics for clarity, detail, aand listener involvement! Simply magnificent. An incredible bargain at its current street price of $550