>> IIRC Dell's 8900 series has a 460 watt power supply and every now and then you can get a coupon on them that saves you a good amount of cash.
so far, i've seen some gtx cards that recommend 600w, and some boxes with 500w, but no 600w.
odds are i'll end up with a PNY GTX 970. i've had a number of PNY GTX cards in the past and have always been pleased with them.
but it seems there are more fundamental questions to be resolved first. such as does a given title even require an "average PC". not all games are skyrim.