Is there a rational for turning up the vidcard, specifically how the settings should be between the Core, Shader and Memory clock? I'm using rivatuner, and I get pretty good results for this old rig, but of course trying to squeeze as much as possible out of it.... 

I'm pushing the Core from default 459Mhz to 525 or so, with the Memory from  defalut 400Mhz to 450 or so.....

I guess the Q is since the Core and Shader will be the same, (as linked in rivatuner when I turn it up) how should the Memory slider go up in relation to the others?  More, same, less..... keep tweaking till I get best results??

I tried a search but couldn't find anything 

With my 9800GT I just use the maximum settings that the computer is completely stable at. There is no link between memory and anything else, just set everything as high as possible as long as it's stable and not overheating.

You MAY be abled to get more performance if you UNLOCK the Core / shader clocks, and raise each individually, however on my card I did not and keep them linked.