Since you're comparing to an RST, you might want to try test-riding some bikes with similar-travel forks that are a bit higher-end (either at a bike shop, or by borrowing a friend's bike for a ride). You may find that a Reba at 115mm or something similar gives you everything you need.
FWIW, I put a 2004 Talas (90-130mm) on my Klein Attitude, which sounds and looks a bit ridiculous. But I was hoping to get a much shallower head angle as well as more travel (that and I picked up the fork for about $150). It's OK, and I ride it regularly, but in retrospect I would have been better off with a Reba or a Fox F100 or something... hill climbing has become a bit more challenging with the high front-end, as well as navigating very twisty low-speed singletrack.
Just my two cents.