Hello,

Being a longtime B&W fan myself, I thought I'd throw in my $.02 just to be helpful
Just for a bit of background, over the last few years I have previously owned the B&W 604 Series 2, the B&W CDM series (the CDM's have been discontinued - but they were a model up from the 600 series), and most recently, the newer 604 Series 3 along with a pair of the 603 Series 3 as full-size surrounds.
To be honest I really enjoyed the B&W's. Nice open sounding tweeter. Solid mid-range for vocals. Nice full bottom end. I thought that overall, they had a really nice clarity for a speaker in that price range. Although some people are not fond of the B&W tweeter, I always found it to be nice and clean sounding to my ears. In short, I don't have a bad thing to say about the 604 or 603's.
I do have a few words of caution though. I actually preferred the 603's to the 604's for music. The 603's just had much tighter control in the bass. I think the 604's traded some of the tightness and control in the bass area for more overall bass output (higher spl's maybe). The 604's were a bit more dynamic for home theater or bass-heavy music, but the 603's were just clearer and more accurate.
Also, I don't recommend using the B&W's with an A/V reciever. There are two reasons I say this.
1) They just seem that they were made to be used with separates all the way. They sound a bit more "congested" or "closed-in" on a reciever (even a great one). I have heard them on Rotel separates though and they really sing. It's not that they sound bad on a reciever, they just don't seem to live up to their potential.
2) (and this is a biggin' for me) , I have a Marantz A/V reciever (SR9200) which is almost bullet-proof. I have run many, many different speakers on it (B&W's, Def Tech, Paradigm, PSB, and Axiom), and the 604's were the only pair to ever make my beloved Marantz kick into protection mode and turn off. This tells me that the B&W's were presenting too difficult a load to the reciever's amp section at that volume. Now, I will say that I was playing Rush (Leave That Thing Alone) at a really high volume level - like kick you in the chest lound - so take it for what it's worth.
Just thought I'd share my personal experiences with the B&W line you're looking at. Hope this helps a bit.

RJ

BTW, after the huge parade of speakers through my home in the last few years, from the Paradigm Studio to the B&W 600 & CDM series, to the PSB 6T's, to the Def Tech BP2002TL's, you wanna know the only ones to stay?

The Axiom M80's