AMD athlon II X2 240, 6 gigabytes of 667mhz ddr2, 600w cheapo psu, gigabyte GA-MA785GM-US2H, Hitachi 1 tb hd 7200rpm, dell 22\" lcd 1920X1080, 6 120 mm case fans, Thermaltake r1 cpu cooler, BFG gtx 260 core 216 (650 core, 1100 mem). Lite-on DVD drive.
For reference.
Unless I'm looking at it wrong, that board only has one PCI-e slot. So you can't SLI anyway. GTX 470/5850 are the most logical upgrades for you. I wouldn't SLI 260's at this point in time anyway, unless you are getting them rediculously cheap.