I have a budget of $3000
= You can build a seriously powerful machine entirely from scratch.
Granted, what you have now isn't really bad. It'll play the game, and with your SLI cards, play it fairly decently.
The 3 major things you're going to want to look at are:
In order to get the latest, greatest CPU, you're going to need a new motherboard. This is also where the new RAM comes in.
the Intel i7-950 are supposed to be coming down in price by nearly 50% sometime in August. I would wait for that, personally. It'll save you nearly $250 from what I hear. They're reaching $580 retail currently.
If you go with that particular CPU, you're going to need a motherboard with an LGA 1366 CPU socket. I'd suggest ASUS or EVGA.
Also, you're going to want to slap in about 6 gigs of at least DDR3 1600 (PC3 12800)
Next, I'd put in a GTX 470 GPU. ****, if you've got 3k to spend, throw 2 in there for SLI.
I'm a big fan of RAID Hard Drive setups. Buy 2 identical SATA3.0 HDDs and put them in a RAID-0 array using your motherboards built in settings.
Soundcard... I've always liked Soundblaster. Latest & greatest usually are pretty inexpensive. Onboard would do too, really.
Can keep your current DVD burner/reader if you're happy with it -- same with your tower case, if it's a decent size. I like full ATX cases.