I say if you want to go cheap, you can always go the route I did. I just used a PC I got for free. It was a 700MHz Duron. It had a sound card and booted and ran RR. Added an inverter and I was good to go. That was a long time ago. I've since upgraded the PC and built a custom MDF case for it. The case can be made for next to nothing. Also, it doesn't have to be ghetto, and it can work. It's just generally easier and takes less space to use a DC-DC power supply.
If you're just getting started, using a freebie old computer and an inverter can be a great, cheap way to get started. Then, as time goes by, add or upgrade to your liking.