It all depends on the software you want to use. I had it working on an AMD K6-2 350 for some time with some freezing issues, albiet, this is probably the minimum for any software out there. I would try RITZ DVB and DVBdream first, as they seem to be a lot less memory/cpu intensive. Then if you have no probs with those, try out Mytheater (the most memory intensive software). For any of these its helpful to install a pile of video codecs first, then install the software.
I currently use a 1.8 gig celeron with 512kb and it seems to be fine with Mytheater.
I believe that the starbox will work on either kind of usb ports, so you should be good there.