I own the N800's and used to drive them with a pair of Bryston 4B-SST's, yes a pair, and they rocked, then I was on the upgrade path, the ML33H's or the ML436' were my target. My wife and I went to a hi-fi show and heard these tube amps driving a pair of N800s, and they sounded way better than any of the solid state gear that was driving them. http://www.octave.de/english/products/PowerAmplifiers/INFO-MRE130.htm
I demoed the Octave MRE 130's with Super Black Box (outboard capacitive storage) and they made my N800's sound like I was in the room with the performance, the music felt more alive, and intimate despite losing some lower end bass compared to the solid state amps, I decided to get a pair. I addressed flushing the bass issue with a B&W ASW850 subwoofer and Velodyne SMS1 subwoofer controller. This has been an excellant combination and the soundstage is awesome. With the sub tapped into the second line out from my pre, I can use the Velodyne SMS1 to fine tune and integrate my sub with the rest of the system.
I am contemplating doing a demo with another pair, I would like to try bi-amping just to experiment and try to see if I get some more additional headroom.
Now these are available in Europe and Japan, and have recieved high marks and reference ratings, in fact the Octave combo HP500SE preamp and the MRE130's went head to head against the ML432 and ML preamp and they were both rated reference class in the German magazine Audio.
I am not sure what your price range is because the pair is 13500euro, about $16875 US dollars at $1.25 dollars per euro. I recieved a great dealer discount and a great trade in on my Brystons; so I did not have to pay that much. They are available in 120 and 240 volts and use 4 KT88's in each mono amp providing 140 watts into 4 ohms. They advertise these amps as being able to drive difficult load speakers, inlcuding the N800's.