New build; a few questions

Hi everyone. I'm planning on building a new gaming PC, with a budget of about $1500, though I can spend a couple hundred more if necessary. It will be used primarily for gaming, though I'll use it for any other applications requiring a lot of power (eg CAD). I already have a Thinkpad so I'll be doing a lot of my day to day computing on that.

I've decided on a few things, most notably the GPU, which is the EVGA Geforce 9800 GX2. I wanted to get some advice on a few other components

1. CPU - I'm trying to decide between the Q9450 and the E8400. One thing I'm worried about is how soon I'll need to upgrade to Nehalem. I would like to keep up a high end (not bleeding edge, but respectable) system, but at the same time I'm not going to spend much more than $400 on a CPU (unless the performance really justified it). So with that in mind, should I go with the E8400 and plan on dumping it in a year and a half if not sooner, or spend the extra $150 on the Q9450 and plan on keeping it 2+ years?

2. Mobo - I've been looking at the Asus P5Q Deluxe (Intel P45) and the EVGA nForce 780i. I'm open to any other suggestions as well. the P5Q is definitely superior, but it doesn't support SLI. I might want to throw in another GX2 sometime in the future, but I won't be buying a new mobo to do that. I'm leaning towards the nForce 780 for that reason. I'd like to get a 790, but I don't think it's worth $350+.

3. Power Supply - I honestly don't know a thing about these other than the fact that I have to get one with enough watts for my system. Should I wait until I've finalized all the other components before looking at these?


Any help will be appreciated.

Newegg links for components discussed:

Q9450
http://www.newegg.com/Product/Prod [...] 6819115042

E8400
http://www.newegg.com/Product/Prod [...] 6819115037

P5Q
http://www.newegg.com/Product/Prod [...] 97&Tpk=p5q

nforce 780
http://www.newegg.com/Product/Prod [...] 6813188024

Geforce 9800 GX2
http://www.newegg.com/Product/Prod [...] 6814130338

Thanks for the anandtech link. I checked out their multi gpu performance comparison and see no reason why I would swap the GX2 for the CF 4870s. Both offer tremendous performance, especially at 1920x1200 which is the resolution I'm primarily interested in. It looks like the GX2 actually beats them in terms of practical performance (ie when not comparing 120 fps to 160 fps). Regardless, they definitely aren't worth the extra $200 so I'll be sticking with the GX2.

One other thing I noticed in their comparisons is that the "GX2 SLI" performed very poorly. This is two GX2 cards in quad SLI, correct? Has Nvidia not released decent quad sli drivers yet?

As for the rest of the build you suggested, I see no reason to use X48 over P5Q or nforce 780i since I don't need CF support. I'm not sure what your reasoning behind the E8400 was. I'm considering it, but my orginial concerns about the CPU still stand. Unless I upgrade in under a year and a half, I think the Q9450 would be the best choice.