You will want to check out the Spectron Musician III amps which are a very popular choice with the 800 series. That's what I use with my 802d. The joule pre is another popular one. I personally use a Cary SLP03 for my preamp.
Best preamplifier, amplifier for B&W 800 Diamond
Buying the new B&W 800 Diamond speakers (already installed). I was wondering who has first hand experience which preampifiers and amplifers sound best with these speakers. Sound quality is the most important issue, not necessarily price. Any feedback would be appreciated!