Good small footprint gaming PC rig help

I'm in the market for a gaming rig, and I know I could build one on my own, but I don't know that much about the process (maybe someone will change my view on this).

I'm looking to get a decent (doesn't need to be cutting edge), set-up with a smaller, maybe portable footprint... something like a fragbox in size. Not knowing which current PC vendors make solidly built systems these days, can anyone recommend a good vendor? Or are there smaller do-it-yourself options available to be built by someone more local to me if I assemble the right parts? In this case, where would you recommend I go to look up the component part options?

Thanks!