Vid card dying looking to upgrade

Hi
I live in Australia an I am currently running the following

Core2 E6600 OC @ 2.85GHz (can go to 3Ghz At least, but it hot here and to be safe)
ASUS P5N32E SLI Plus
kingston DDR2 1066 RAM 4x1G CL5 KHX8500D2K4/4G @ 5-5-5-15 950MHz (Note due to MB dont think I can run much higher only got it as it was dirt cheap)
XFX 8800GTX
Silverstone 650W

The Problem is the 8800 GTX might be on the way out (which I will be looking into)
Now I am thinking that if the card is failing I will not only replace it I might also
upgrade the CPU as well.

Firstly my current MB is unable to support the newer Quad cores due to a massive Clock up
by Nvidia and incompatibilities between the chipset and the architecture difference in the
newer Intel Core 2 Quads, so the upper limit is the E8600 for this MB. But would it be more
cost effective to get a e8400 over the 85 or 86?

And Secondly what card would be the most suitable for the E8400 on a system such as this that
would hopefully be a significant enough improvement over the 8800 GTX.

And yes this is primarily a Gaming rig

Feel Free to comment on the Current setup as is (except for the RAM) 2+ years old now and am interested in what
people think of my choices back then. Especially with using the OCed E6600 with 8800GTX.

I would get a E8400 and OCing to 3.8

http://www.newegg.com/Product/Prod [...] 6835103065

Also if you have a rez of 1680x1050 a HD 5770 or HD 5850 if your rez is 1920x1080 HD 5850 or HD 5870


hope this helps

The older quads are supported e.g. the q6600 & q6700 but I don't use too many quad core optimized apps or games and the older ones are damn hard to find.