Upgrade Processor for XPS 700

About 6 months ago, I expressed interest in upgrading my processor. I just wanted something that will keep me relatively on pace for the next year or 2.

Well, I was wondering if someone could help me. I was wondering what options I have for upgrading my processor, preferrably inexpensive, but I'm sure my options are limited. Here's what I got:

Stock XPS 700

E6600 processor @ 2.4 GHz

GTX 275

3GB Ram

I'm sure the RAM can use an upgrade, and I hear a possible option is the WM543 Conroe XE Kit, X6800, 2.93Ghz, 4MB, 1066FSB, B2. Would the $500 be worth the upgrade, or is there something better anyone can recommend? Dell parts also recommended a 3.8GHz 800FSB P4 Prescott, but the $1000 is a bit steep. Any advice would definitely help.

Thanks for the help!