ATI 4878, 4870 or 4870X2 or 4890 Crossfire

[MILINTICA]

I have already chosen my CM, CPU and Ram.
Asus P6T Deluxe
Intel Core i7 940
2 * 2 GB DDR3.

And I use the Antec 1080 case.

I plan to make a raid 2 * 500 for the system and 1 to 2 * for storage. A prior I would feed on a 850, although I think it's a bit much. But where it gets stuck it to the graphics card. I expect to play recent games with the best quality. It is a pc to make me happy So.
The question : It is worth to taking a 4870X2 ?
Can I take a single in 4870 Then according to my needs, buy another and make a crossfire? I direct or darkens a 4870X2? Knowing that the 4890 comes out, what choice had I?

[Bradan]

Why not go on for your triple channel RAM? Then I take a X2, not much more expensive than 2 * 4870 basic, especially as buy a 4870 later, they say and then we do not because there is more at that time.

[HAMAKO]

It depends on your screen if you have a nice 30 "a 4870x2 or 4870x2 4870 (to be comfortable) see a gtx295. After 4890 the cross of the air to poutray good but not enough power available for testing give a real opinion if you choose this option => attends modified versions.

[MILINTICA]

I'll stay with XP, I know, shame on me, by then. Xp manager that does 3 go, I think to go from 6 (ie 3 * 2) in 7. But unnecessary at this time.

[TACY]

The problem not from windows xp or seven but only the 32bit version ... managed to more than 3GB of ram you have to go in 32bits (windows xp 64-bit managed very well over 3GB of ram ....)