With a sensitivity of 90dB/2.83V/m, the B&W DM603 S3 is a fairly efficient loudspeaker. Back in the day I would drive my New Large Advents (approximately 87dB/2.83V/m) with a 40 watts per channel Harman Kardon reciever and it was plenty loud to get the neighbors to complain and sounded pretty good. However, now I am of the opinion that one cannot have too many watts to achieve good sound, I dunno, dynamic headroom? I currently run 400 watts per channel to stacked double Large Advents.

Another problem is specifications alone cannot tell you the whole story. One manufacturer's amp rated for 70 watts per channel could actually output more music than another rated for 100 watts per channel. Then there are audible sonic qualities that largely become a personal preference. However, for those speakers I would want my amp's specs to be something like a minimum of 100 watts per channel, both channels driven into 8 ohms at 20-20,000 Hz and 0.05% or less THD.

I think you don't have to look much farther than the Cambridge Audio Azur 840A. Although, there are plenty of options for intergrated amps at that price. Its tough to make a decision if you can't audition.

Oh, I forgot about the Creek Classic 5350SE for $1500. Pretty darn good.