I'm building a PC as cheap as possible for a friend, and I figure the cheapest way to go is to buy a used pc off ebay and add a cheap GPU such as an RX 460. I've found a PC for $100 with an i5-4570 and 8gb RAM, which is perfect, but it only has a 255W PSU. Thee RX 460 has a TDP of 75W and the...