What's a good cheap power supply. it needs to be at least 350W
What will it be powering?
an old PC i will be refurbishing.
Right, but what components? Something like a CX430 would be great here.
Depends on your build's estimated TDP and the GPU, but I like these for the price:
Past that, look for the SeaSonic S12II, Rosewill Captsone G, and that XFX P1 around $55.
With the $20 mail-in rebate, the Antec EarthWatts Green 650W 80+ Bronze at $50 is most likely the best deal. But it might be wasteful if you don't need the two 6+2-pin PCIe cables for those 'higher-end' GPUs.