What angle is the seat at right now? My bikes are around 22 degrees, but some of the fast crowd seems to like angles in the 10-15 degree range. And yes, lowering the seat can make a big difference in cruising speed. One thing to watch for is that your center of gravity not get moved back too far. My rule-of-thumb is for my shoulders to be ahead of the rear axle by at least an inch or two, so you're not unweighting the front end.