I have a couple of dell GX270's I bought from my school district for $1 each. They run mach 3 and techno's interface great. I do all my designing on a custom built quad core q9550 3.8ghz desktop with a nvidia GTX 260 video card.

The computer that runs mach doesn't need to be a workhorse. If you do 3d design work, a faster comp would benefit you.