Your system is better than you're giving yourself credit for.
I'd start with the speakers to finish off your 5.1 setup. QS8s are amazing, and virtually eliminate the need for 6.1 anyway. The VP150 is great, but unless your room is large I'd buy a VP100 and get a few extra DVDs.
The Denon 2200 will be the last player you'll need to buy for years, and plays everything wonderfully. Pioneer and Onkyo make universal players that are cheaper, but the Denon is well worth the extra bucks.
As far as your display, the X1 and Z1 are both great buys, as is the Hitachi Home-1. You might also save your cash for the Panny or Sanyo Z2, which offer big performance improvements. Get out and audition.
Your receiver is more than adequate. At the worst, if you decide on the VP150, you may need a monoblock for the ever-starved-for-current center channel.
