Need some upgrading advice

[Patchwork Neurology]

Since I'll be receiving my tax returns soon I figured "why not upgrade the pos of a pc I have".
Only issue is I'm not really sure where to start, so I figured I'd ask the people over at [H] for some help. System consists of:
-Asus P5N-D
-Pentium D 820
-4GB Crucial ram
-BFG 9600GT OC
-HDD's, 600W PSU, Pioneer Blu Ray, yadda yadda yadda...

I'm sort of stuck on deciding to upgrade either the cpu or gpu. Keep in mind I am in a sort of a bind and can't really spend more than $200-250. Which component upgrade do you guys think would get me the best performance results? Welcome to any suggestions!

Also, I have never done any sort of water cooling before so i was also toying with the idea of just purchasing some wc components and oc'ing the shit out of the system. But since I'm new to both water cooling and overclocking I'm not too sure. Please give any input/suggestions you guys might have. Thanks!

Oh btw I posted this in this section because IF I do upgrade my gpu I would prefer to go with Nvidia particularly because they're the only cards I've ever used and never had a problem. I'm not a fanboy really I just feel more comfortable using a brand I'm used to.

 

[Mega666]

Easy - put a core2 in it.

 

[Excalibur55]

Easy - put a core2 in it.

+1

Your Pentium D will bottleneck any new card you will put in your system. It might already be bottlenecking your 9600GT. My own Pentium D will be doing the same for my 4650 (but I can live with it...).

 

[cannondale06]

yeah upgrade that cpu to core 2 and get a gts250 1gb. if you sold your 9600gt and old cpu then you could easily keep the actual upgrade cost well under $250.