Slow speed is one thing...the card I'm using running at 1/4th of it's potential is not. Also moving the cards around has proven that the problem can be fixed somehow...that was back with only two cards though.
As for the PSU this is the one I got.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817703037
I also got a watt meter, and at full load, it draws 950 watts or so. So basically I've got 250 watts of overhead.

As for the problem happening before with only two cards, yeah, that was annoying, but somehow swapping the PCI-E port of the two cards fixed the problem. *shrugs*
The reinstall happened when I installed the third card, but yeah, before the install, everything was working just fine. Also, the computer doesn't shut down, I just get a black screen with nothing on it. The computer is still on, but no video feed is being sent to the monitor.