if you are doing regular line drawings in autocad, graphics should not matter one bit.
once you get into 3d modeling and rotating, 3dorbiting, materials, and all the good stuff, then YES, graphics becomes important.
but, 3d on autocad has always been very lacking. 3dmax, maya, rhino, are much better 3d programs, but those need good video cards.
RAM is a big part too.. more ram can never hurt. w/ each new autocad version, they add more and more CRAP so that its...