TUF armor on the back? That seems silly. The one thing I have not liked on my P67, that they continued again, is the placement of the assist fan. Renders the top pci x4 slot useless.
I was using Xigmatek 1000 rpm fans (can't recall the model number). They were fine until I put the GT AP-15's on the GTX120 on the rear. Then the GT's just starved them and my temps went up.
So after seeing the video on Martin's...
The 650D is a good choice for water cooling - especially if you like modding your case. Stock fans are weak, but easily swapped out. A good site for WC gear reviews is Martins Liquid lab. Ton's of great...
You'll be fine. CPU magazine tested a Seasonic 650w psu using two GTX 580's and it ran just fine. 670's use less power. I believe the TX650 v2 is a Seasonic.
If you do decide to upgrade I can tell you that you won't need more than...
The oldest card that I am certain will work is a 7900GT. Still use it to bring up new computer when I build them since mine are always water cooled. I have a Radeon 9200 AGP card, but have no idea if it works anymore.
Have you checked your bios settings to see that everything is normal or as you had it originally?
I'd also get rid of the sickleflows (had one,it sucked as a rad fan). Put on a pair of Gentle Typhoon AP-14's and get better, much quieter...