Windows 7 - Asus GTX 560 framerate problems

Hey guys I really, really need your help.

I had a GTS 250. Games were running smoothly on high settings on 8x AA until suddenly every games ran below 20 FPS. So I bought an Asus GTX 560 and I thought everything will run smoothly again. But I was wrong. I'm still getting below 30 FPS - even on 4x AA! I'm assuming the culprit's my 500W CoolerMaster CPU?

I looked around the internet and found out that my card should have been connected to two 6pin connectors. My PSU came with only one so I plugged the other 6pin that my card came with to two 4pin molex..

My system runs on Core i5 760 and 4GB (2x2 GB) RAM.

Both the old and new card requires a 600 watt power supply.....So low power could/maybe be the problem.....

That's what I suspect as well. Or maybe it short circuited or something because I used to play NBA 2k11 on 8x AA on high settings, crowds, bench, players, etc with even hi-res texture packs. Now it struggles even on medium settings on 4x AA..

But how can I tell if it's a PSU failure or a motherboard failure?

A power supply loses about 10% of it's output per year..,..The only way is to try a known good 600 watt power supply, also those molex to six pin adapters are problematic as well....

Thanks, man! I'm looking out for some good PSU's now.. I really hope it's not the motherboard..

At stock speeds 560 Ti requires 500 Watt PSU minimum, not 600.