As much as it pains me to suggest this - I have to weigh in on buying new. I just started helping out at an LBS and had no idea how big the whole "gravel grinder" fad has become. I'm not looking to buy myself, but if I were now is certainly the time. Given your lack of space there's a lot of benefit to owning new, starting with low maintenance and lower risk of component failure.

I personally bought a new Surly Cross Check as a commuter this summer, and have been very pleased with it as an all-rounder that I don't feel compelled to keep spotless. Raleigh, C'Dale, Jamis and many others are debuting really very nice bikes this year, many with disc brakes, some with the new SRAM hydraulic disk/brifters.

My free advice, and worth every penny.