I like flat handlebar bikes with a 56cm top tube.

My 15" Mongoose has 56cm ETT (effective top tube) as did a 1999 18" Trek 4000, so they both fit perfectly but the goose has about 1.5" more standover than the Trek.

Looks like both the Trek fx and Fuji Absolute have a nearly 55cm. I'd probably go with those personally and get a longer stem if necessary.

It might take you a while to figure out what ETT fits you best. You also need to figure out what back angle you'd like. 20 deg from horizontal for a racing posture, 80 degrees from horizontal for upright pleasure cruise, or somewhere in between. For upright you may want to go shorter ETT but you may need to swap stem or bars to get lost bar height back.