*Something* has to be the bottleneck in the system, but the faster your
video card the better the performance no matter what your other components
are. Of course if you are running a 9700 Pro on a celeron 1ghz you would be
much better off with a CPU upgrade over getting a 9800 pro though heh.
I don't see how a P4 2.6ghz could really be called a bottleneck at this
point, that is a darn fast CPU.
A friend of mine just put a non-ultra 6800 in his old Athlon XP 2400
Thoroughbred, and it's running rings around my 9800 Pro matched with an
XP 3200+ Barton.
The CPU may be a bottleneck but that's relatively insignificant, the way
you can usually tell is if you get the same benchmark results regardless
of resolution. So your CPU has become the limiting factor, that does
not negate the performance gain of a faster card. So when you benchmark
Doom 3 with a 6800 you get 70 fps at 1280x1024, at 80x600 you're still
getting 70 fps, with a much faster processor Doom 3 benches at 75+ fps
at 1280x1024 but now at 800x600 you're getting 110 fps. That's not all
there is to it, but for the most part you get a reviewer who runs a few
tests notices the above situation and reports that the 6800 will be
limited by what CPU you have, it's true but...
well here, Guru3D has a pretty good article comparing a P4 2.8 GHz with
an Athlon 64 3800+
http://tinyurl.com/4smnb
So a new $700 processor and motherboard will get you 5-14 more fps at
1280x1024 depending on the card (though the 2.8s speed is eminently
playable).
And if you look around Guru3D some more there's word that the regular
6800 GTs can be soft-modded from 12 pipelines to 16. Making them an
even better bargain.
My last two cards have been Radeons, I don't consider myself a fanboy of
either company, but right now I can't help but recommend people give the
6800s a shot. You can't go wrong right now spending $200 or less on a
128 Mb 9800 Pro either, that's an excellent value and all the current
games are playable at high settings, albeit at 1024x768 resolution.