There's currently a bunch of 75w peltier's w/ heat sink and fan going on ebay for $15. I got two, and will use them to cool my water right before it enters the water block. Too risky for me to put under the waterblock. Plus a 1 gig needs like a 100w pelt anyway.
No, 75 watts is just too small for a T-bird. You wont see very much difference in temps from your air cooled setup and you will be dumping a bunch of heat into your case from it. For a T-bird you need at least a 156 watt pelt to see any real drops in temps and a pelt that big will need to be water cooled. An air cooler just wont handle a large pelt.