$500 gets you a marked-down Masi fg bike at Bikes on Wheels if I'm not mistaken (probably am). Components might be **** but who knows, could be a good deal. IRO is proably the only frameset option in your budget. Shops in the neighbourhood will have access to IRO, Surly, Soma, Cayne (Uno), Fuji, Bianchi, Kona, etc.

PS. Don't get the Urbanite, ask Somnambulant for reasons.