Which is the weak link?

Hopefully this will get answered here.  I am looking to find the weak link of my system which comprises of the following;

Pioner PDP4280XD Plasma

Pioneer VSX D2011 Receiver

Pioneer 757Ai DVD Player (CD duties too)

Mountain Snow Component cables

Quad 22L2 Front

Quad L Centre

Quad 11L Rear

QED Silver sprkr cable to all front

QED Flat spkr cable to rear

Movie soundtracks sound good to me - fast and accurate, although the centre can sometimes sound like it has a little too much mid-range, e.g. Charlton Hestons voice doesn't sound quite as deep as you think it should.

Music can sound a little 'forward' in the mid-range and sometimes a little 'busy' on guitar based stuff like Snow Patrol, although I am unsure as to if this is down to production rather than system. 

I am unsure if putting in a good CD player (Cyrus/Arcam) would be wasted, given the receiver.  Or is it down to cables?  Not sure where I can go next but I am sure something is holding back the potential of the system.

Any comments?