phantomcow2

you want the specialized hardrock disc. Its msrp is something like 550 i think, slightly over but if you can squeeze a few more pennies ide go for it. Assuming your fork is disc ready, you can go the more economical way and have just disc in front. That is where you need the most stopping power anyways. For under 100 you can get a machine made front wheel of reasonable quality. THen add another 70 for an avid BB7 and there you are, discs. Replacing only the hub means buying new spokes more likely than not, basically a wheel rebuild which is a another complication and will run between 35-50 in most instances.