More amps on the 12V rail will not cause issues. You just need to make sure that everything your running does not exceed the 12V rail or your PS will die an early death.
Which in your system you are building, you will have ample room for upgrades. Up to 2 GTX470's with a motherboard that is has a 20 4pin additional 8pin for CPU.
BTW, the price for you power supply is 139.99, the 40 mail in rebate is only if you mail the form in on time, correctly filled out and with the UPC code cut off the original box and thus making it so that you can only return the new power supply to thermaltake for warranty replacement. The mail in rebates are never a sure thing and often take 2 months for the return.
At least these are the reasons I never consider the mail-in rebates when figuring out cost of purchase.
