Good luck with rdram. It's not really in use any more and expensive, at least compared to ddr ram. Personally, I figure out what you need then hit ebay. Your probably going to be looking at 100-200+ dollars to add 256 or 512. Sounds like a good excuse to buy a new PC to me. You can probably get another dell without monitor, keyboard, etc. for under 400 dollars. Just my 2 cents...........

Newegg does stock RDRAM and they are excellent for buying pc parts.