My "touring" bike is a Specialized Tricross Expert that I'm using for light/cc touring. I'm 5'9" and it's a 54cm bike. Regarding 56 or 58, or a little big vs a little small, I'd go with a little small and get a longer stem if necessary. 58cm seems huge to me, FWIW. Also, my first mountain bike was a size larger than it should have been, but I bought it anyway. I always felt like it was too big and that I was wrestling with it, so I won't make that mistake again.