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I got this one very cheap second hand.
The costs I could save wouldn't match the costs for a new PSU.

Yeah - you'd have to be running a bigger rig to see effects more often - but, for the sake of efficiency you might as well go 6 - 7 Gpus.... DOOOOO IT :3. I'll be at 7 soon (tomorrow) if my mobo/os cooperates.

My board has exactly 2 PCI slots :D

I will see if I can find an upgrade somewhere :D

Yeah - if you are also trying to everything on a super tight budget you might consider a m.2 to PCI-E converter to get an additional gpu on your board if that is more financially more reasonable than getting a 6-7 mobo. I heard it can work, but I cannot speak for yours specifically.