I have owned the Yamaha MX-800U for 28 years now and do you want to guess where I have it set up?......In it's original box in storage. Do you want to know why?.....Because I thought it was the cat's meow up until I started to LISTEN to other amplifiers. I used it in conjunction with the Yamaha CX-600U pre amp. (I now use the CX-600U as a pre amp in my DJ set up). The major thing that I always noticed in almost ALL Yamaha audio equipment is the sound produced was very upper-mid-range-y and brittle highs and a very unnatural unmusical sound. The only audio equipment that Yamaha ever produced that was great were their recording decks. During the cassette tape days, I tried a lot of different decks including the famous Nachamichi decks and the Yamaha's blew them away. The same goes for Yamaha's CD recorders. I tried a few different ones and the Yamaha's make the best CD recordings of them all. So I praise Yamaha for their recording equipment! BUT, this MX-800U is a different story. I have been using Paradigm 900se 2 speakers for 21 years now. An absolutely great pair of speakers. The best $3,000 I ever spent. The absolute best thing I can say about the MX-800U is that it does have a snap in the bottom end. A real punch. But the rest of the sound it produces is not worth sitting down for. It is a rather visually striking amp as well. In 2004, I heard what was eventually going to be my new and still present amplifier, the NAD C 270. I use it in conjunction with an NAD C 160 pre amp. Let me tell you, the sound of the MX-800U can't even come close to the NAD C 270! The NAD's presentation of the music was mind blowing! The NAD C 270 is an extremely musical amp. BUT this comment is not about the NAD C 270. I have held on to the MX-800U over the years just in case I need it as a back-up amp. However, I have a very nice Pioneer Elite A-35-R that will do the trick much better than the MX-800U will. So I'm considering selling the MX-800U. The MX-800U can be the right amplifier if one likes very bright, ear fatiguing, and unnatural musical sound that just get's in your face and annoys them.

I bought my MX800/CX800 when I lived in Japan (1986-1990) upgrading from the Yamaha M50/C70. I still have both units and whether your listening to your music soft or loud - this thing is as pure as the driven snow! Built like a tank and very quiet. I've tried other amps but I always seem to migrate back to the Yamaha. Only wish is to upgrade the speaker connectors in the back but other than that, it's been amazing for me. Right now I'm using it via an Emotiva DAC/Pre out to some B&W 602 S3s and it's simply breathtaking. At times I'll add in my old JBL L112s (also purchased in Japan) and the place rocks! If you get your hands on one you won't be sorry!
Best!

I have owned these CX-1000 & MX-800 when I was in Japan back in 1988,I had it every since as of today 05-2015 these pair served me well, I listen music every weekend for the pass 25 years,without a single problem what so ever, I also have owned many others high end,like Luxman, etc. nothing come close to this, the music is so clean and clear the dynamic is astounding you could hear every notes using 3 pair Klipsch speakers and I'm very please with the quality with top notch Engineer to create these thing,I could bought MX-1000 to go with it but the spec.is the same except more power rating.
Up until now I could not even crank it up pass 1/4 the volume, regardless how loud you crank it up the music is still clean, in front I hooked up with a pair of Klipsch RF-72II,in rear
has Klipsch RF-82II and other Klipsch SB-52 all at once, with Yamaha Hi-Bit Technology D/A converter is awesome and was developed twenty five years ago sound so good.

One of the best built amps of that era. Bulletproof,built like a tank and quiet as a mouse.Worth every dollar I paid for it.