Have a Dell Dimension 8200 with 512MB RDRAM (2X256 PC-800 @ 40ns - Samsung). I want to upgrade to 1G RAM. Found 4X256 PC-600 memory (don't know XXns). I'm thinking that it would be best to use all the same memory so I'll simply replace the older memory (and perhaps keep my eye out for RDRAM that are an exact match to what I have now). With the PC-600 being older and slower, how much of an impact in performance will this cause? I do a lot of digital photo and video editing so trying to weigh speed vs quantity of memory. Thanks for your help!