There really shouldn't be background noise or lack of "clarity" (I don't know what you mean by that, but its hard to have a vocabulary for audio). All your stuff is respectable. Just looking at the prices paid, the Cambridge 340A is the lightweight here, but from the speaker efficiency you should have enough power for all but the most aggressively loud listening (or a very big room).
The biggest factors (in order) the determine how a system sounds:
1. Speakers
2. Room/the recordings
3. Electronics (DAC, pre-amp, integrated amp, power amp)
4. Wires (interconnects/speaker cables) and rack
5. Isolation
I'm not a fan of B&W, so many drivers, or alumimum drivers. That said, B&W makes quite respectable speakers for people that only know what music sounds like via other speakers (not live/unamplified music). This is not a slam against you polar316, it just reflects where you are at on your audio journey (the same place most of us started at).
Make sure the speakers are pulled out into the room (hopefully at least a couple of feet) and turned towards you. Next sit between them and not against the back wall. Hopefully the room doesn't look like a warehouse (big with very hard surfaces) and the bulk of your recordings aren't from the dawn of digital (early 80's, some very harsh sound back then made it onto CDs). Hard surfaces can be taken care of with wall hangings, carpet, or acoustically room treatments (see the acoustics circle below).
But my guess is that you're problem is with isolation, mostly from power abberations ("dirty" power). Are you located in an older part of town? Ratty old overhead power cables, older factories nearby, old electrical service in your place (with fuses)? Does sound quality change throughout the day/week/holidays? Being in an apartment can be much worse. Digital in particular is very sensitive to dirty power. If you have an MP3 player, try plugging that into your system (will probably need an adapter port) to confirm. The quality of the source is less than a CD, but try switching back and forth between the two with the same music in synchronization.
Solutions to dirty power range from a under $100 to thousands, depending on how bad the power is and how much you want to clean it up. Good luck and let us know what you find.
