My studio produces cross-platform but most work is performed on MacPros. The consensus among my IT PC consults was to avoid Vista as long as possible, especially if photography is your game. I tend to listen to those more knowledgeable. Plus, my studio cannot afford workflow breakdowns. Considering I started my computer career on a PC and Photoshop has always been a Mac-friendly app, maybe you should take heed to those fantastic Apple commercials where the fat, PC guy fails to light his Vista sign. Absolutely brilliant.
Jeff Schewe was kind enough to post Scott Byer's blog address: http://blogs.adobe.com/scottbyer/
Be sure to read: PSWorldPerformancePresentation_Expandedhttp://blogs.adobe.com/scottbyer/PSWorldPe...on_Expanded.pdf
Scott includes PCs in his discussion and I think Scott's PDF is one of the most important "performance" articles out there. These treasures are indeed hard to find.
Just asking, as my knowledge of an optimal set up is not that great.
Take more time with your research and comb the forums with a fine-tooth to steadily build your knowledge. The information is here and there, and photographers tend not to enjoy repeating themselves. Performance and cpu optimization hasn't changed much in the last year.
If you were on a Mac, I'd suggest visiting Macgurus.com. I have no idea if such a site exists for PC/Photoshop users. They have a plethora of great technical information.