If you will buy new gpus anyway why don't you just buy the rx series , why hd and r9s they are not power efficient i don't recommend them if your electricity price isn't very cheap, you can buy 3 rx 470 4gb and 700 watt psu will do fine , maybe a mobo with 3 x 16x pcie and forget this raisers , just mount your gpus directly onboard , any cheap cpu will do fine , and 4gb of ram is ok.
Also: you don't need all that hdd space
Thank you, well I don't pay for electricity, it's in the rent no limited for me, it's students flat. Yeah I could buy some new cards, but it cost a lot for start. I have money to buy them, but I just wanna try it with some older and cheaper setup and if it's gonna work for me I will buy new ones.
I've read that it isn't good having more GPU in x16 PCIE on mobo because of heat.
The 320GB HDD is already in the PC, I have no idea if it's SATA ATA or whatever will see once it arrive.
PC I've boughtAlso what you think about mining merged cryptocurrencies? XMR+FCN
Thanks.