Keep in mind that a true SS is a little more efficient than a derailleur'd bike that you just never shift. Most SS's [should] have a perfect chainline and no idler pulleys to roll through, and reduced weight without an entire cassette, extra chainrings, derailleurs and shifters. My SS is a lot easier/more fun to ride than my geared bikes are when I just don't shift.
Get a SS/FG, you won't regret it!