Ok, right now with my bike, i am having horrible problems with my brakes, im having to adjust before a ride and during a ride and every 30 mins or so so it wont rub horribly or squeak like a dying rat. and ive read reviews on the brakes i have and they are notorious for this problem..

I have a Gary Fischer piranha, that have Hayes MX2 Mechanical disk brakes.
I am looking to upgrade to the Avid ball bearing disk brakes - i can get them for about $55 so its not a huge expense, my question is though, will it be a direct swap out or will i need a different rim/mount, etc to make it fit?

Or would it be a better idea to get a set of hydraulic disc brakes?