New 7770 on 300W PSU?

no way:

here it is the minimum settings:
http://www.amd.com/us/products/desktop/graphics/7000/77...

"500W (or greater) power supply with one 75W 6-pin PCI Express power connector recommended "

it may even work but not for long, there are much variables, like capacitor aging, and your psu with time starts to low efficiency.

buy a 500W psu from corsair and you are good to go. you will probably burn your gpu with that 300W psu.

It may work - HD 7770 is max 80w. <-- Not much at all. I wouldn't risk it though. Grab this PSU - it's the best for the price because it's on sale right now.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

It will most likely work just try it out you have nothing to lose i it works for you then it's good if not get a new PSU simple as that.

No need to waste OP money on a 500watt PSU for suck a low end system a CX 430 is plenty LOL Please remit you statement about needing a 500watt PSU for such a low end system.

i'm just recommending what AMD is recommeding, if you check the website, you will see that this graphics card requires minimum a 500w Power supply, so unless he have a really good brand 430W, it is not good to play with graphics card, i saw a lot of Gpus burn because of Generic psus.

of course you can go with a corsair 430W:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

but i would say, for true safety and log time run, i would go with:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
if you need to upgrade something later you will already have the psu.

Thank you all for your quick response, my PSU is old, it has +5 years, so i think i will get an 6850 and a new PSU.