That motherboard is not SLI compatible, so going Nvidia will not work (at least if you want to add a second Nvidia card.) I don't even suggest the GTS 250. At that price, it's almost a rip off. The GTS ranks 22nd on our GPU performance list, while the 5770 ranks 16th, and they cost the same. You can do Crossfire with that board, and another 5770. There's also the advantage that the 5770 is DX11, while the GTS is only DX10, leaving you with a better card, for the future. Not sure if I would choose that PSU either, you could get a better one at about the same price.
Newegg.com - Rosewill Green Series RG700-S12 700W Continuous @40°C,80 PLUS Certified,Single 12V Rail,ATX12V v2.3 / EPS12V v2.91,SLI Ready,CrossFire Ready,Active PFC"Compatible with Core i7, i5" Power Supply
That's 80+ certified, and only cost $70. Gives you 150 more watts. Has a large single 12V rail (54amps), which SOME say is more effecient, and safer (I don't know if this is true or not).
EDIT : Hard drives pull a VERY little amount of power, changing from a HDD to and SSD won't give significantly less power usage.