I run my games at 1440x900 with EVERYTHING maxed out on HL2, CS:S, Bioshock no problems. 202 CS:S stress test score.
The 4000+ is not a bad proc, overclock that bad boy, hopefully you have good RAM, DDR has dried up. I've seen my DDR500 ram on ebay, but at $200USD for 2x1GB.
The Opteron's kick @$$, I overclocked my 165 from 1.8 stock to 2.7 no problems. Sisoft Sandra rates exactly to an FX-60 dual core, I don't even think I would bottle neck a GTX, and if I did, it wouldn't be by much.
I have a 939 4000+ right now, overclocked from stock 2.4 to 2.85 ghz. Paired with a 7900gt, I can play all my games like bioshock,fear,hitman, stranglehold etc on 1440 x 900 resolution and high settings. Im thinking about getting a 8800gts so imagine how much of a boost in fps that would give.
My old P4 3GHz was bottlenecking my 7800GTX, so yes it is bigtime! When I first played Doom 3 on my P4 3GHz + 7800GTX I couldn't run any AA or run ultra texture quality, but now that I have my Core 2 E6600 @3.7GHz I can run 8xAA and run ultra quality textures.
it wont by much. especially considering most games can still take full advantage of only one core, and even then, the performance improvement from 1 to 2 or more cores isnt huge for gaming yet, youll still be limited by the gpu most times, unless you turn your resolution and details down. then your max fps will be limited by the cpu more.
otherwise, again, no.
@systemlord... a P4 at 3.0 is only going to be fast enough to run smoothly at lower settings as you saw, since its performance is noticably lower than a 2.4 4000+. a P4 3.0 is more or less on par with a s462 3000+ @ 2.0 that a relative has (which is also poor for gaming), since they were released around the same time too.
to give an example, the X2 3800+ i have, is still fast enough to play older and newer games pretty easily, @ stock even (my 7800GT 256 is beginning to be overwhelmed a bit though). the biggest improvement however, is going to be in the amount of memory the OP has, if the OP has less than 2GB of ram, then thatll end up being a problem for gaming most times now, much more than their cpu will be.