I believe you can just put 1 card or max 2 (would be risky imo but I may be wrong) with a 650 W PSU .. because most of these cards have a minimum requirement of 500 W for the PSU mentioned on them (that would include the mobo power as well). So if you could up your budget for the card to about 23k then you could get a r9 280x . But then again this PSU wont do any good with that. The 280x gives about 700-750 khps I believe, from what I had checked online last about like a month ago.