Get an i5...same price as the Phenom IIs while being slightly better for gaming, lower power consumption, and runs cooler.
As for video card, don't get two GTS250s - those are 9800GTXs rebranded. Two of them are good, but for the money you're better off getting an ATI 5850.
If this is for a gaming machine, a fast dual core would be better than a slow older quad. Has this been purchased already? If so, is there any budget to replace the CPU?
Yeah, it's already purchased, @skora, you said it would be better, but would it still be okay. Let me put it this way, I have an evga 9800gt superclocked, would I notice any difference... lets say in Crysis by switching to 2 gts 250's?
I would expect the SLI setup to perform better but not much since the CPU will probably be cramping the GPU subsystem before you can stretch the legs of 2 GPUs.. BUT, I wouldn't expect 2x250 GTS to do that much better than a pair of 9800GTs. If the 250s are purchased also, I'd seriously consider selling them and the CPU, then using the money to get a new CPU and a second 9800GT. If you haven't bought them, spend the money on a second 9800GT and maybe the Phenom II x2 550.
What games are you playing? The time of buying a high clocked dual is as good as over. look at some of the latest CPU core scaling charts. Your best bet is to replace the CPU with something like the phenom 2 X3/X4s or one of the cheaper athlon 2 x3/x4s. What sort of budget are we looking at?
------------------------------Dell response:
"I am glad I am the one who received your request as I am going to do my best to assist you."
Reply to mi1ez
Not too much of a budget, as I had to sell a few things to get some parts, so I'm broke, will that CPU do for now, in a couple months I'll be able to get something better. an i7 perhaps?
I play l4d, crysis, crysis wars, crysis warhead, fallout 3, dead space, etc.