what is the best computer for running autocad on?

That can't be answered - too many variables, including what does "best" mean? Fastest? Most reliable? Personally, I think the choice of graphics card and monitor(s) are more critical when talking computer aided design programs.

See Between the Lines: AutoCAD 2009 System Requirements

any gaming specs will surely be good with your autocad processes.
good luck!

any gaming specs will surely be good with your autocad processes.

That is NOT true. CAD/CAE and gaming have different requirements. The better graphics cards for CAD, such as the $3150 PNY Quadro FX5800 or $2000 ATI V8650 are not good gaming cards, nor do good gaming cards make good design or engineering cards.

Do NOT buy a card designed for engineering with the expectation you can game well with it. Two totally different tasks - two different hardware requirements.

Gaming requires;
CPU resources
Graphics
Memory
Hard drive space

Gaming reqiures;
CPU resources
Graphics
Memory
Hard drive space

HOWEVER, these resources are used somewhat differently depending on the (primary) application.

Gaming is best run on a machine with a fast CPU, high end graphics speed and resources, and of course memory.

Auto-Cad requires more CPU resources (CPU speed is not as critical), memory ~can~ be less of a requirement (depending on your patience), and again hard drive space availability.