The folks at Videoguys.com really embrace the idea of being a value added reseller. Beyond offering a wide array of video production hardware and software at great prices, the web site is packed with articles and information to help you best utilize the latest tools at the lowest cost.
Here's the link to recent article which lays out everything you need to know to build your own Quad Core workstation. Why build your own? Because you can save a lot of money - minimally hundreds of dollars.
Note too that they caution against using Windows Vista: "As we've posted in other area of our website, we simply can't recommend Vista at this time. The 32 bit version is a recourse hog that brings nothing to the table for video editing. Vista 64 bit is more powerful, but good luck finding drivers for your hardware. It's not a pretty picture. I know that someday (hopefully soon) I'll be singing the praises of Vista 64, but for now we still stand by our recommendation / warning - DO NOT RUN VISTA for your NLE workstation!"