I had a similar question in regards to the build I am doing on a Trek 560, except that I was starting from the other way around. I was considering Shimano brakes sets, but then I became aware that at some point Shimano incorporated a system in their brakes that used spring tension in both the caliper and the lever. The operative point lies in the energy needed to most effectively move the cable in both directions through inertia and drag in the sheath. The intention behind the design is to create greater sensitivity and more incremental modulation in the applied force. Well, I already had a pair of unsprung SunTour aero levers, so I sought out a set that did not come designed to complement a springed lever. (I bought a set of Tektro R556.) For what it's worth, I ran the solution past the owner of my LBS, and he nodded in agreement. My guess is that whatever the mix and match, there would not be a dramatic difference, but I wanted to dial in the best effect in the first shot.