I'm going to suggest hitting up your local LBS and getting your first bike from there. IMO, you shouldn't order online unless you know exactly what size you need. You will be able to ride the bike at the LBS and see what actually fits.

I see Specialized Langsters, Bianchi Pista, Kona Paddy Wagon, and some built Surly Steamrollers going for under $600 and even in the $450-500 range. Yes, it's a little more expensive, but you will be sure of the fit, you will get free repair work for a year or more, support a LBS, any warranty work will be better, etc. Just my 2 cents.

Case in point:

http://www.bikeforums.net/showthread.php?t=526185