What would you do?

I need to upgrade my computer, but dont want to spend that much money... What's the best thing to do with about $200??

Current Specs =

CPU: P4 630 (Single-Core 3 Ghz with HT)

MOBO: Asus P5LD2 Rev 1.0 (which means the BEST cpu that I can get is a Pentium D... I need Rev 2.0 to get a C2Duo)

RAM : 3 GB DDR2-667

GPU - PNY Nvidia 9800GT 1GB (I'm guessing my performance here is limited because of my CPU?)

PSU - 500 Watt Thermaltake

OS - Win XP 32-bit

Mid-ATX size case

also, I have a Seagate 750 GB Hard Drive I just ordered as well.




I want to spend the least amount as possible just to hold me over for another couple years... I've read that quad-core isn't all that necessary yet? Even with games? The main 2 things I do is surf the internet and play a couple first-person shooters... COD4, Team Fortress 2, and I am really interested in buying Modern Warfare 2 when it comes out next month...

So should I buy a budget Dual-Core w/ motherboard combo, get a cooler and try overclocking for the first time? Or go for the AMD Phenom II X3-BE? Also... is 667 RAM way slower than 800? What would you do?