Dell Dimension 8200 RDRAM confussion

Dell Dimension 8200. Pentium 4, 2.46 ghz, purchased 10/2002

From my research it appears I would need pc800 RDRAM RIMM ns40

>First: does that sound correct (because DELL gives conflicting info)

>Second: I would like to add 1 gig, DELL has 512MB  modules at $370 each (YIKES and NOT sure if it is correct or is the older ns45).

On the net I have found this particular RDRAM as low as $ 20 (ebay) and as high as $ 200 plus....I am completely stumped on what is best.

I have found some refurbished SAMSUNG for $50 for 2 512MB...and unbranded with varying warranties for around $100. I have read here that these MBs are pretty finicky, so is it better to go with refurbished Samsungs or something new. Are there other brands or unbranded that people have used with success?

Any particular vendors people trust (the ones listed most here often don't exist anymore zipzoomfly., spongebob and Crucial doesn't carry rdram)

PS: I have two sticks of RAM currently installed (factory)  for a total of only 512MB, do I leave them in the first two slots or do the 512MB each need to go first??