Avid fr5 levers should run you $15 or so...good levers.
I upgraded from the stock shifters/brake lever combo and tektro disc brakes to sd7 levers and bb7 discs.....didn't think I'd really notice, but its like night and day.
Go for the discs, and get good ones.
The tektro's were a pita to adjust, and the bb7's have on-the-trail-no-tools-needed-adjustment.
Totally rad.