I think everyone telling you not to mine either has no understanding of how mining works or they are just trolling.

I asked the same questions, ran the numbers, then bought some cheap 5850s... they have more than paid for themselves by this point and also got me a few more GPUs.

Everyone saying "mining is unprofitable" are probably mining right now and don't want you to take all their coins as if they will be able to prevent all new miners from entering the market.