Mark,
You seem to be already quite knowledgeable about audio cables, so I'm not sure if my comments will be of any use.
Usually, one can expect soundstage, and even the perception of brightness or grain, to vary from one recording to another. A revealing sound system will do that, so I'm not sure whether swapping cables will help improve the sound of your system to any significant degree.
From the components you have listed, I would personally stay with copper, especially with your budget in mind. I would choose cables from name-brand companies, such as AudioQuest, Cardas, or Transparent Audio. Those are my favorites when cost is of no consideration, and I need to control system brightness.
For me, cost is always a consideration, a big one in fact, so I would try River Cable (http://rivercable.com/) in your case.
From my experience, I don't begin to hear a significant sonic difference among cables in systems costing less than six figures, but maybe that's a limitation of my hearing more than anything else.