Avid SD-7s or Shimano XTs are the two I'd recommend. I have both on a couple bikes. I'd also say Avid Ultimates if you've got the cash. They're hella nice brakes. Either way, get a good set of compression-less housing. Avid make one with a red sheath which covers the cable between cable stops creating an semi-full housing run from lever to caliper. And replace the stock pads with some Kool Stop salmon colored pads.