Oh and you mentioned non linear setting turning your characters into prezels... the key to working with spline animation is to keep your keyframes nice and spread out. I like to keep a minimum of 4 frames between spline keyframes, but it's all relative to the overall length of the motion. Also, try to throw in a spline break from time to time when things get really twisty...those will break the curve of the motion. A spline break is good to put in at the actual impact of a punch or the landing of a jump.

Hope this helps.