The need for more power is mostly dependent on your listening levels. If you're speakers have some big impedance swings, more current/power can help.
If you listen in the low 80's dB range (average volume) with musical peaks toping 90 dB, that 80 watt integrated is probably as low as you'd want to go with those speakers. More power probably isn't going to hurt. That said, you've got plenty of juice there to drive those speakers about as loud as most condo's I've been in would allow. 90+ dB is more than enough to piss off your neighbors.

Unless you're room is rather large tend to agree with NickWH. You're unlikely to hear a noticeable sound quality difference at all but the loudest levels just by adding a beefier amp. And adding a higher quality amp would be rather expensive, and still might not make things much better, if at all.

Most speakers I've heard don't really sound better at lower volumes just because an amp has more power capability, but there are some speakers that break the trend - they aren't the most amplifier friendly. Large current draws and low sensitivity speakers aren't a good combo for low wattage amps. As you increase the volume you could be taxing your amplifier and of course your speaker isn't going to perform as well if the amp runs out of current.

Hard to say if that's happening here. 80 watts is still quite a bit of power. I don't have experience with those speakers - might want to ask some other B&W owners. Hopefully you can test an amplifier out before you commit to buying one. I'd hate to drop a bunch of cash on more power only to find out it doesn't make a difference at all, or only made a difference at volumes you never play at anyway.