They need a lot of current to drive them properly. Watts don't really count. I drove mine with 130 Watts / channel receiver and they sounded okay, but with music or video that had successive loud passages, you could hear and feel the amp run out of power as it could not replensish the output stages fast enough to satisfy the 802's.
I replaced the amp with a BAT VK6200 in a home theater system and have not had that problem with this amp. They were quite picky on setup (toe-in, distance from rear wall, etc.).
They are very good speakers, but like most B&W products, they will reveal the weakest component in your system. Makes for much trial and error changing of components - an audiophiles dream for some - a pain for others.
I don't think there's a fixed recipe for success with these speakers. My advice is to find components that have a sound that is described with words like, "smooth," "warm," etc.
Some people like them with Krell equipment, I have never like the combination myself. The Krell's do have the power to drive them and provide a good bottom end, but I find the sound a bit sterile with somewhat of an over emphasis of the high end.
They also benefit from bi-amping or bi-wiring. Mine are bi-wired and you can hear a difference between the bi-wired connection and using a single wire. Mid-range is clearer and the high-end has more detail. Bi-amping with a good components provides another step up - a small gain in my estimation, but it can be heard. I tried it with the VK-6200 as it has 6 amplifiers to play with, but in the end went back to a bi-wired setup.
One last caveat. I never believed in the idea of needing to break-in a speaker until I owned these speakers. I will tell you that until these speakers were turned on for nearly 100 hours they didn't sound very good at all. In fact, I almost returned them to the dealer. I took his word for it, and left them turned on every day for 15 hours per day for 3 weeks. Totally different speaker after working for that period of time.
They still need to "warm up," and sound better after being used for 30-45 minutes than they do when the system is first turned on. Mainly, the bass output increases in both clarity and output level.
They are very good speakers, but - be ready to put some time into them to get the correct setup and component match.