Advice needed, to upgrade or go new?

Hello Readers,

I am looking for a little advice on what I should do with my computer situation, in preparation for GTA IV that’s coming out. I am trying to keep a fairly low budget so a good performance to price ratio

My current gaming rig is:
AMD 64 3500+ socket 939
MSI K8N Neo 2 Platinum
Xfx 7600GT 256 AGP
1GB RAM
500W OCZ PSU

Parts that I was just given the other day:
Intel core 2 duo E6300 with Asus mobo
2 spare cases

So here are my questions, would building up on the E6300 become a more powerful rig then my current gaming rig or would the processor (even overclocked?) become the bottleneck and the handicap of a system with the following parts:

DIAMOND RADEON 4850 512MB GDDR3
OCZ 4GB PC2-6400 Dual SLI Ready EPP
Cooler Master eXtreme Power 500W PSU

OR should I just upgrade to 4gb ram and the video card to Radeon 3850 512MB in my current rig?

OR do I just wait a bit for Nehalem to come out and get a discounted Q9550 with mobo as well as the other upgrades?

If there is another better option please let me know.

Messudy

The E6300 will be much more powerful than your current rig, especially when overclocked....I don't think there would be much of a bottleneck either with a 4850. The only thing I would recommend would be a slightly better PSU; 500-600W and with better efficiency.

The motherboard is a Asus P5B Deluxe http://www.asus.com/products.aspx? [...] =11&l3=307

Would this be a better PSU? OCZ 500W StealthXStream Power Supply
http://www.ocztechnology.com/produ [...] wer_supply

Thanks for your input so far guys.

The budget is tight but a little headroom is always good so to be safe should I go with

OCZ 600W StealthXStream Power Supply http://www.ocztechnology.com/produ [...] wer_supply

or for 10$ more should i go for OCZ GameXStream 600W Power Supply
http://www.ocztechnology.com/produ [...] sli_ready_