What type of math are you planning on focussing on? Theoretical or applied? As someone who got an undergrad in applied math I can tell you that having a desktop with a ton of computing power can really come in handy. There is nothing worse than trying to get something done waiting in the queue for time on university computers. Having said that, keep the six core AMD now and wait for either Intel or AMD to come out with there 8 core chips. The FLOPS on those could be just what you need.