Possibly dead motherboard

So, the for Christmas I recieved a GTX 660 (non TI) and I put it in my computer christmas morning and had it running for a little bit, then while testing it out with some Planetside 2, my computer shut off all of a sudden. Since then I have not been able to get my computer to stay on past the windows login screen and more recently at all. So I had thought that my crappy 575w Logysis PSU had finnaly given under the new load of the 660, So I went out and bought a new 600w Thermaltake PSU and put that in my computer. I have only been able to get into windows once with no graphics card in it. Then I tried it with the card in and it got just past the BIOS splash screen and locked up. The next time it locked up on the splash screen, then it locked up halfway through loading the splash screen. By that time I figured I had better clear the CMOS to make sure there wasn't any old settings messing it up, and since then I have not been able to get it to POST or anything, all the happens when the power button is pressed is the lights and fans come on, and thats it. I am at this point thinking that my old PSU took my motherboard to the grave with it and just wanted a second opinion before I went out and bought a new mobo now too. Thanks for the help! 

System specs:

ASRock 880gm-le Motherboard

8gb DDR3 1333 RAM

AMD Phenom II 840 @ 3.4Ghz

500GB Seagate Momentus XT (boot drive)

1TB Western Digital(?) storage drive

and before the 660 I had a GTX 550Ti

The situation does not sound good captain. I think you are down to 2 things, the motherboard like you think or the RAM. What I would do is pick up another set of 2X4 RAM identical to the RAM you are currently using and swap them out. If everything is still bad then when you replace your motherboard you now have 16GB of RAM which is never a bad thing. No harm, no foul. Good luck and let us know how it goes.

Alright, so yeah, I just replaced the motherboard and everything is running great now, really happy with it. Thanks for the help!

Glad it worked out. Sorry it was one of the most expensive parts but who said life was fair?