New video card or new mobo/cpu?

If you need to make a change now I vote for new mobo/cpu/memory.
8800 GT is still a good card.
Bloomfiled is coming out in November. Initially it will be expensive.

You have a reasonably well balanced system now. Don't go overboard on either the mobo-cpu or vga card route, unless you can see your way clear to upgrade the other half later.

I think I would go the cpu/mobo route first, and see how you do.
An E8400 will drive the best single card out there well. Only if you run FSX or supreme commander would you want a 3ghz quad. A P45 motherboard should cost you about $80.
Don't pay extra for features that you won't use.

4gb of DDR2-800 ram is all that you can reasonably use for games. There is no need for more unless you are a heavy multitasker while gaming. Vista home premium-64 would be good. Don't pay extra for faster speed or better timings, it isn't worth much.

If you find that you want more, then I suggest that you market your 8800GT and buy at least a 4870 or GTX260 to get a significant jump in capability. With a 55nm tweak supposidly coming from Nvidia, I would opt for a EVGA card to preserve your option to "step-up" if a better card should arrive within 90 days.
---good luck---

It is not clear to me what would be best. It depends on your resolution, games, and eye candy. I have found the following charts and discussion to be most helpful:
http://www.guru3d.com/category/vga_charts/
There are some cases showing 9800GT-sli which should be equivalent to your proposed 8800GT-sli.
Where do you want to be to get good gameplay?

In general, I like a strong single card because you avoid the game dependent effects of multi-gpu scaling. A 8800GT will go for $85-90 on e-bay. Add that to the $150 cost of a second 8800GT and you can get a GTX260. If you are going to upgrade your mobo and psu anyway, it will cost you less for a single vga card system.

My current PSU does support SLI, but I am going to be purchasing another PSU for the new mobo/cpu - I'd like to keep my old equipment for upgrading my HTPC.

I am thinking of purchasing the E8400, a nice Asus mobo I found on newegg and 4gb of ram and seeing how that works out with the 8800GT. If I still want more, then I'll sell the 8800GT and get the GTX260.

2 8800 GT's will last you at least to the next generation of video cards. In SLI the pair is very powerfull and paired with a 8400 CPU it will rock your games. Good luck whatever you choose.

Here are some charts regarding 8800 GT sli:
http://www.anandtech.com/video/sho [...] =3341&p=13
http://www.anandtech.com/video/sho [...] =3341&p=14

MoBo/CPU/RAM ALL DAY!!! that is still a great video card, ur current setup is probably bottlenecking that 8800GT right now, let alone a better Video card.

Go Intel, E8400 or 8500 and get at least DDR2 PC 6400 800 MHz ram with low timings or better.

Ps. Get another 8800GT and SLI them if you have the leftover $$$ though you will need to get a decent power supply as well...

Thanks for all the replies guys - I've decided to go with the E8500 and a Asus P5N-D mobo - I also got another 8800GT on eBay for $100 for a nice SLI setup. Thanks again!