Couple of months back a friend asked for a Revit config. Some of my observations :
1. Revit viewport doesn't use more than 1 or 2 cores (only final rendering uses all cores).
2. Get an Nvidia card. Intel Graphics are bad and preferably avoid AMD Radeon. Although I believe only the AMD mobile radeon cards were having driver issues; desktop cards were probably ok. Of course if you find a cheap FirePro/Quadro workstation card, nothing like it. Revit does not use the GPU for rendering, only for the viewport.
www.revitforum.org had a lot of helpful info including user benchmarks with different configs.