Setting up new machine - Advice needed please

[Altsoba]

Ok, after going through lots of posts here, I came up with this:

INTEL CORE I7 920 (2.66GHZ) SKT 1366 BOX (D0)
ASUS P6T DELUXE V2 ( 6Slots, Socket 1336)
ASUS GTX295/2DI 1792MB DDR3 PCI-E
CORSAIR KIT 6GB DDR3 1600MHZ DOMINATOR (CL8)
CORSAIR HX-1000W
INTEL SSD X25-M 80GB MLC (G2) SATA 2.5" (R 250MB / W 70MB)
COOLERMASTER HAF 932

I'll be running Windows 7 64 bit and two monitors.

My questions are:

What kind of performance can I expect from this kind of machine? Can I have a maxed out main with 4 minimal alts and still run 250 fps (joke ) in Isle of conquest?

What would you change, if anything?

Thanking you all in advance.

EDIT: Was recently adviced to put instead MSI Radeon R4870X2-T2D2G-OC, better and about the same price. What do you think?