680i Killed two of my GPU's

i used to have 2 8600gts Gpus in sli, after a while, the gpu in the slot closest to the Cpu started to over heat, and i threw it away, then i got a single gts250.

last night i added a perfectly fine, working gts 250, to make it sli, and again the gpu in the pci express slot closest to the cpu started to overheat crazy.

i took the gpu out and put it in the other pci express slot and it worked fine, unlike my 8600gts it hadnt been in that slot long enough to have permanent damage.

how could this happen?
DAMN YOU XFX ><
is it the pci slot?

i have the latest drivers, and a 750W Brand name power supply.


id appriciate some help, as im on tigerdirect right now deciding between 750i sli or 790i

so the motherboard doesnt have any problems?
B/c i have a cooler master case with 9 fans 120mm fans, and 2 pci slot fans.
my case is always under 28 degrees and my cpu is 36.

I have a few questions before we get to the nuts and bolts here.
Why did you throw out a perfectly good 8600 just because it was overheating?
Why would anyone run 2 -8600's in SLI in the first place?
Why would you buy a GTS250 and try to SLI it with a 8600?
I ask these questions because...
An overheating card is easy to fix, it is almost always not a problem with the card at all, but more a problem with your setup, the card is full of dust, or the fan on the card may have quit working, you are pumping too much voltage to the slot, or the airflow in you case is simply bad. Anyway, all easy to fix.
A single higher end card like the GTS 250 will outperform 2 weak cards in SLI, like the 8600's
And lastly, to SLI 2 cards, they have to be the same card, or family of cards at least.
I did not think (and I could be wrong) you could SLI a GTS250 with a 8600?