Snow_Owl...
You need to demo, demo and demo again
IMO (with very similar music tastes to you and as an owner of B&W 685's (theyre in my bedroom set-up) i dont think you could go wrong with a decent Arcam or NAD amp.
Again, IMO id stay away from Denon, C/A, Cyrus and Naim. With the 685 speakers, those amps all sound too clinical and i really dont feel the Naim has a good sound with B&W speakers.
If you want to stay under £500 for an amp (which in turn will leave you some £££ for a CD player upgrade) then personally i would be looking on eBay for a decent Arcam alpha 9 or 10 integrated amp, an Arcam A85 integrated amp and if you want to go for a new amplifier then take a look at the NAD C352 or NAD C355BEE integrated amps. Both can be bough from Superfi (www.superfi.co.uk). Believe me; both those NAD amps and any of the Arcam amps mentioned above will sound superb with the B&W 685 speakers and will provide the power that they need to be driven well and sound at their best!
My bedroom set-up consists of the B&W 685 speakers on Atacama SE24 speaker stands (mass loaded with Atabites), the NAD C352 amp and the NAD C542 CDP and it sounds superb.
The bass is deep and puncy but not OTT, the midrange is brilliant, well timed and detailed and the treble is sweet and crisp. Great for the vocals on Hed Kandi CD's and absolutley brilliant with Fischerspooner/Layo & Bushwacka. The sound really makes my bedroom rumble haha...
Let us know how you get on!