You'll be using a software called Mach3 most likely. Just about any desktop and most laptops manufactured in the last 5 years will work fine. The best deals for used computers are found on eBay and craigslist. As for the BOB, I don't know anymore. I once used Axxus BOBs, but they are no longer in business.
To get better answers, ask this question in the Mach related part of the forum found here: Mach Software (ArtSoft software) - CNCzone.com-The Largest Machinist Community on the net!