B&W 801 vs 803s

Two issues with the 801 Nautilus: (i) they do in fact require a big room because of their prodigious bass and your room may be too small, and (ii) they require a ton of power, to the point of needing to be biamped with big solid-state, which means an amp that uses feedback (and thus all of the problems that feedback brings).

That said, if I had a huge room, listened only to rock/pop (i.e., crap multitrack recordings of electric instruments), and didn't have a lot of money, I would definitely consider them - great bass and boom.

Palermo100: You misunderstand me - by "boom" in the context of the 801, I mean thunderous dynamics, not what I suspect you refer to, which is one-note bass from a poorly designed ported speaker. The 801's are great in that regard, assuming they are driven properly, which I again note means bi-amped with really beefy solid-state amps (the speaker cannot be properly driven by a single "normal" muscle amp like a Bryston 4B - it needs a ton of power).