My 7900GTX is runing hot

[MAD450r]

Meh, this is getting out of hand
My advise:
If you really want to get better cooling for the 7900, then
http://www.arctic.ac/en/p/assistant/vga/chip/147
or
http://www.overclock.net/t/1203528/official-nvidia-gpu-mod-club-aka-the-mod

As for the PSU...
PSUs "age" , and not always very well... loss of 10-15-20% per anum -depending on usage/load- must be suspected... meaning: a 5 year old PSU is more likely to kick the bucket at full load compared to new.
That is what happend when you put the 780 load on it.
Your Truepower 2 is at least 5 (8?) years old and even when new would not have been able to handle the 780 (or a 680 or a 580 or a 460).
Its time to switch the Antec over to light duty, eg fileserver only and put a better PSU in

This is what jonny had to say about the Antec 2.0 550
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=22

Well I just got a 580gtx used for 100$ and yes it works 100% fine on my old power supply and has been gaming at full 1680x1050 res without a hitch and no I did not change my powersupply.

I still plan on saving to build an i7 over the next year.

this 580 doesn't even trigger the PS's fan to high so I guessing this ps is powering it just fine.

 

[RnRollie]

suit yourself
suggest to plug in all info in this http://www.extreme.outervision.com/psucalculatorlite.jsp
-dont forget to put cap aging at 30%- and see how much power you really need/use, and if the Antec is up for it.

Just by putting in the CPU , RAM & the 780 -not even counting harddrives, fans, cdrom, & bling the recommendation is a +500 watts PSU I'm sure if you put in all the other stuff (drives, fans, etc) you'll exceed the Antec 550