New build

Hi,

What do you think of this build: http://uk.pcpartpicker.com/p/pQLvkL
For light pentest and hash cracking. Is the r9 290x and CPU best value for it's buck? What mobo do you recommend, as I may want to add more more GPU's in future. More ram? Got a large case to futureproof all later upgrades in.

Budget of ~£1.5k, can go higher.

Thanks.