I have used N 805 speakers for about 2 years (longest audio equipment has ever stayed in my house, excepting my Rega Planet).
I have used several amps, and will give you the long and short of them all.
I will definately say that I would recommend tubes in some form. I started off with a Conrad Johnson Pv-11L Tube preamp (just 2 relatively inexpensive tubes, needing to be changed once every couple of years) mated to a McCormack DNA.5 amp. MARVELOUS COMBINATION.
You should be able to find a CJ PV-10 (lower model, but there is a certain magic that the 10 has that the 11 lacks, but the 11 is infinately more detailed and refined (and discontinued). I can recommend the Conrad Johnson PV-10, PV-11, and PV-12 preamps. The PV-11 is older than the PV-12, but the PV-10 has been around a while too, but is still made. COnfused? Good. CJ preamps are good stuff, with a nice sound. The McCormack DNA .5 amp is the stuff of audio legends (cheap legends anyway) in its day it was regarded as the budget piece to own. You could find a DNA .5 for less than $800 for sure. The Used CJ preamp would be something like $550 for a PV-10, $650 for a PV-11 if you can find one, and $750 for a PV-12.
Again, you really need to get a nice tubed piece in your system. AFter a while you'll never go back to a pure solid state system again.
Next I sold My McCormack, and got an AudioPrism Debut tube amp (not enough bass without a sub, but damn, did it sound nice). Then, I went temporarily crazy, and bought a really, really nice sounding solid state integrated amp, which I definately recommend to those who have not yet tasted tubes. THe Audio Refinement Complete. It's made by YBA (they have nice SS stuff) It has a remote! It sounds really nice! It should cost about $600 used and its all you need!!
Next, I had to get back into tubes, and I got a Rogue Tempest Integrated amp, which, up until that moment, was the best compromise of all. Totally tube, really flexible, with all sorts of inputs and outputs, nice remote, it looks cool, sounds like a million bucks (it really does) and best of all, Rogue Audio (Mark Walker and Mark O'Brien) are the absolute nicest guys to ever start an audio manufacturing company. They are the coolest. Mine might be for sale in the future (keep reading), but I believe there is one here now (without all the cool tubes I have) for $1450. I know, I know, too much $$, but it sounds incredible with my Nautilus 805s!!!!
So, I have this Tempest, which, like absolutely rules, but I just got a Jonze to try a particular amp, the one amp that has eluded me, and wouldn't you know it, I scored one righ there last week- The Cary Sli-80 Signature.
Now, initial comparisons give the nod to the Cary, but I'm going to be doing some serious comparisons and tube rolling, and one of these amps is going to be the winner once and for all. (there has been some hot debate re: which is better with the B&W 805) N E Way, IF you are at all curious about tubes, I urge you, learn more. They really do something to the music that makes it sound more like music and people really sound. IF you are not interested in the magic (but somewhat increased hassles of tubes, my recommendation would have to be the Audio Refinement Complete integrated, or a Musical Fidelity A3Cr amp (absolutely the best SS amp I ever heard, but I did not hear it in my system with 805s) mated to a preamp you like.
Good luck, and dont forget to go and seek out the tubes!!!