I've been looking into getting some new hardware to possibly help make Vegas 11 run better. I've been thinking about getting everything from a new graphics card to a complete new system. And I found the following website's guide tremendously helpful in making some decisions. It has some specific recommendations for NLE's in general, as well as Sony Vegas Pro.
http://www.videoguys.com/Guide/E/Videoguys+System+recommendations+for+Video+Editing/0x4aebb06ba071d2b6a2cd784ce243a6c6.aspx
http://www.videoguys.com/Guide/E/Videoguys+System+recommendations+for+Video+Editing/0x4aebb06ba071d2b6a2cd784ce243a6c6.aspx