Keep the Treks- buy a used Ultegra 10 or 11 speed group off the 'Bay and upgrade the 520. Probably run you about 300 for the groupset. Buy a decent set of wheels for under $200. Or look for a donor bike on local CL and strip the wheels and groupset off of that, sell the frame and whatever you don't use. You can also sell the stuff off your 520 for a good amount of money to subsidize the upgrades.