Stick with the Seagate drive.
a pc with a r9 290 in it needs 650W. Get a good one per -
http://www.tomshardware.com/answers/id-1804779/power-su...
eg XFX 650, Seasonic 620 or 650, Antec HCG 620M
For a non k cpu, you only need a H97 motherboard.
For another few dollars you can get gskill 1866 ram