CPU 25C, mobo 47C ... those temps are very cool, many systems get hotter (much hotter) while just idling. If your system is crashing then there is a problem, but it looks like your temps have nothing to do with it.
You need a fairly mighty PSU for best stability, especially if you have a heavy GPU. You might be able to squeak by with a 750W or so, but 900W or more would be better, it depends a lot on your GPU and CPU overclocks.
I'll assume that all the power connectors on your mobo and GPU(s) are being used. If not, then you need to plug them all in right away, lol.
Can you list exact models for your PSU, DDR3, GPU(s) and any other cards? And, since you're worried about temps, what kind of chassis (and extra fans or cooling accessories) do you have?
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams
[/Korth]