What components can i underclock for mining?

[StealthyCactus]

Im in a bit of a pickle, here are my system specs;

CPU: FX 6300 with Corsair H80
Mobo: Asus Sabertooth 990FX
Case: HAF X (4 200mm fans, 3 120mm fans)
GPU: 2X R9 280X direct CU TOP
PSU: Corsair HX750


I have an old 7870 i have lying around, and im considering popping it in for a 400KHs boost. Im concerned that 750 watts isnt enough for the power draw of my system due to all the other various componenets that i have. So far i calculated with these 3 cards i need around 755 watts.

I was wondering, what can i Under-clock to take some pressure off my PSU for mining. I dont really game too much, i just use my system for mining/school work. So far im planning to undervolt/declock my cpu to 3.0ghz, and lowering core frequencies on the GPU's/increasing memory frequencies.

Any other possible ways to shave off power you guys have in mind?

-Thanks!

[vm1990]

depends if you mine scrypte coins then you need another PSU. but sha256 coins nock down the memory frequancy as far as you can on the gpus

the only other option is buy a cheapish PSU and have a 2psu system