I myself am considering the B&W 684s which I demoed last Thursday with a Marantz 6003, Yamaha A-S500 and a Rotel RA05se.
Marantz -
Very good sound inregards to treble, symbols so and so. Where as bass I thought was a little light for me, and not very warm which I prefer. I found it to be very clinical and didn't control the bass very well with these speakers.
Yamaha-
Heard new notes and a wider bandwith with my music with this amp but not much else I thought. It sounded like to me it was trying to satisfy all aspects the senses but wasn't outstanding in any. I found it to be very soul-less, not to my taste.
Rotel-
This being the least powerful but my God! This was in another league, I was told that Rotel amps go very well with the 684s and they were right! Instant hit was the punch of that bass as well as not over bearing on the treble. Mids were lovely touch and bringing music to life like I was sitting in a theatre rather than a science lesson.
After the demo, the bloke at the shop said that a magazine did a test on the actual wattage of these amps which came to about 80wpc. Also, he did add that the RA04se would sound better due to not having a remote control and a few led lights.
I am going in again to demo these but this time with the RA06se which is on sale for £450! Mind you, it is ex-demo but bargain I think.