Also bear in mind that TEC coolers are designed to work at 16v......more than a computer PSU puts out. They'll RUN on 12v, sure, but at about half the cooling efficiency. And you have have have have to cool those as well, you can't just stick a TEC somewhere in the cooling line, and run it un-cooled, give in a day and all the connections will melt.
Thomas is right on the power draw. Not all are alike, but in general, a TEC plate will draw around 24 amps, tho I've seen some older ones that cut off at about 20 amps. Note that this is not dependent on usage! They draw that much from a cold start, no matter how hot the CPU its cooling gets. Given you already have a watercooling system that's powered off the 12v rail, I would look into getting a supplemental PSU just for the TEC. http://www.crazypc.com/products/7250.html
is a place to start looking, and don't forget the relay switch to turn it on with your regular PSU. Just remember, that's still a 12v PSU, so a TEC module rated to transfer 70c will only do around 30c.
Which Swiftech block did you get? Those need to be mounted in a specific direction related to the processor socket, otherwise they work like garbage. Given that you're seeing temps that high, doublecheck that you have it in the right orientation.