Action shots with K-X

Is anything other than a 2.8 zoom in the 50-200, 100-300 or something else with at least that reach, going to get me good stop action shots under indoor, typical college gymnasium lighting? Most occasions I'll have to shoot from the bleachers, but sometimes I can get court side. My cheap Pentax FA-80-200 has acceptable results, as long as the players are standing still that is. A new 2.8 is out of reach right now with just a $400-$450 budget to work with.

Am I making any sense?

P.S I really want to stay with Pentax lenses.