If you like the Synapse, you shouldn't have trouble finding others to compare it to. Most other manufacturers have similarly-designed frames. Ask for "endurance" type models. Some call them "comfort" frames, but be careful with that term, as it can also mean cruiser types, which you don't want. Trek has models with their H2 and H3 designations (meaning taller head tubes than their H1 frames), Jamis has their Xenith Endura and their Ventura lines, Felt has their "Z" models. There are many to choose from. Scott, Raleigh, Giant, even Bianchi. I just got a Synapse Alloy 5 for the same reasons.