Hayes MX2 XC mechanical disc, they're 45$ at bikesmart.com. Not quite sure if they're good, haven't tried them myself. But it's a Hayes... I wouldn't worry about your bent rim, it won't affect a disc brake. Hmm, maybe you should invest a little more and get the MX1 XC for 60$. If stopping power is what you really want, consider a front 8" rotor. It may be unusual to see an 8" rotor on a xc bike, but hey; it's going to stop you.