The ML335 is enough for *any* speaker that requires only two channels of amplification. Period. In fact, unless you have it on a 220-240v power line you're not supplying enough amps to get it to full rated power at 4 ohms, no less lower impedance.
If you insist on sticking to B&W speakers, IMO the 803D is far better for music than the 804D. The 804D can't really do 40Hz at loud volumes; the 803D gets a lot closer.
If you insist on sticking to B&W speakers, IMO the 803D is far better for music than the 804D. The 804D can't really do 40Hz at loud volumes; the 803D gets a lot closer.