Ditto what Kathi said!

I also ride 650's on my road bike. I've never had an issue finding tires as long as I'm happy with 23c. I have found that finding wider tires are usually a bit more of a challenge, but for a road bike, 23c's are usually fine anyway.

I have no difficulty keeping up with the smaller tires. Like everyone else said - when the fit it right, it makes all the difference.

I've only had 1 flat (in 3000 miles) and it was last weekend on a century. It happened as I pulled into a rest stop (nice timing, huh?) and the bike shop SAG guys at that stop actually had a spare 650 tube for me! (So I still had a backup for the rest of the ride).

I know nothing about the Trek bikes - but congrats on what ever you decide to purchase!