FrankHarveyHiFi:
I've always tried to make a thing on these forums (or any forum for that matter) about driving speakers properly. Many people buy a nice expensive pair of speakers, probably because they've always wanted that specific pair, and continue to drive them with their existing amplifier, with little or no consideration as to how well the two go together, or whether the speaker is being driven adequately.
If you really want to stick to an integrated amplifier, you can see how an ATC SIA2-150 would match in with the B&W's. Otherwise, I'd drop in a Bryston power amplifier and give the B&W's a good kick up the rear and get them doing some real work. Bryston amplifiers are capable of what seems to be limitless power, and a grip on the speaker that most amps can only dream of. They also have a knack of sounding exactly the same whatever the volume they're played at.I take your point that budget speakers will sound better with good amplification, but they'll still sound like budget speakers. I'm not denying the the amps you mention may be good, but would be overkill.
Far better to allow the system to live up to its potential and upgrade the speakers now. Sonus Faber Is a good suggestion, too.