I am thinking about buying a used R9 295x2 to stick in a HP that only holds one GPU. I have a 620w PSU in that build. I have 2 semesters left to utilize the electric in college dorms so that power guzzler is really the single greatest hasher I can put in a single PCIe slot. Downside is electric is not cheap in my area and I will be stuck with this card over the summer, I don't think the electric grid in my room could handle that card in one computer, my main computer doing mining when not in use with a GTX1070 which isn't too heavy, and an AC. After I graduate next fall the 295x2 would make for a good room heater at least.
My biggest concern though is that after a year from now the 295x2 won't have any resell value when somenewer GPU can severely beat it on efficiency and still do good on performance
Iv had 2 of them,DO NOT USE IT FOR MINING!! OMG...so many problems with both from thermal throttling (max was like 28mhs/gpu) and melting psu cables. not to mention using 700-800watts mining.you could run 6 rx470s for that power! do yourself a huge favor and crossfire 2 RX480's at the very most if you feel the need for dual GPU's. 31mhs each and nice gamers.personally i prefer the rx470's. good luck!
So much for the 500 watt TDP, and only running a GTX 1070 right now I simply do not know if I can run the power limit at 50% on AMD cards like I can with the 1070 and go efficient. That 620w PSU wont be handling that in this case
Not to mention I question if the card has resale value after the year of use is up. I can't do dual RX480's in that HP though. If the RX490 were actually out that would probably be the smart purchase for this but they may as well rebrand that to the 500 at this point