I am searching for a used CPU and GPU for my PC. Are there any risks for the CPU if it hasn't been overclocking or working on high temperatures and I put a thermal compound and use a good cooler (not the stock one) after buying it? Besides from getting out from a mining rig and the temps, is there anything else I should watch for while buying a used GPU? Does it worth the risk in buying a second hand GPU? I am considering to buy an HD 7770, 7790, 7850, 7950, 7970, R9 270X or 280X or at least Nvidia GTX 900-1000 series from the older ones. Or should I turn around and think about RX 570-580 old/new?