Go for the ebay, IT's cheap. the most important thing about the size for ebay is the standover height and the top tube. Make sure you have about a inch of clearance. The top tube is a tad bit more trickier, but I would suggest you go into a bike shop and try out bikes. Measure the top tube of the bikes that feels comfortable. You can always change the stem, so don't make that an issue when buying from ebay.
Good luck.
Some older models that I would suggest other than the same old same old Trek 520 is the Miyata 1000 from the mid 80s & Schwinn LeTour from the 80s & Novara touring bike & Nashbar 5000 touring bike(tange 2) & cannondale st800. You can get great deals on these older bikes. IF you don't mind doing some upgrades. These bikes are absolute steals.
MIyataphile