If you're doing rendering in a multithreaded application (like 3D Studio Max), then multiple cores and hyperthreading would be helpful. On the other hand, most CAD software is singlethreaded, and won't benefit significantly from that stuff. Therefore, if you're just doing CAD, get the processor with the highest single-core performance that you can afford. (If you've got a big budget, this is going to be a quad-core, hyperthreading Core i7 anyway...they have a turbo mode that increases clockspeed dramatically when some cores are idle.)
Check the
certified driver lists before choosing a video card. It's all in the drivers—the hardware itself doesn't matter very much for CAD work. Anything midrange with good drivers will be adequate for most teams' needs.
I'm not a fan of small screens or low resolutions for CAD...I'd reconsider that if possible.