my request is which upgrades will yield greatest percentage increase in performance.
the upgrade of RAM will probably go to 3 or 4 GB with most of that assigned to RAMDisk
It's either a RAM upgrade or videocard, your pick. Whichever will net you the best performance.
If you're going with a new videocard, if you can afford it, go with a X800XL
which has the best performance/cost ratio right now. It'll whoop that X800Pro while keeping up with the 6800GT.
If you're going with a RAM upgrade, then make sure to check how many DIMM slots there are on the motherboard. Also, make sure the memory is going to be compatible with the new sticks you've got in mind.
Keep in mind that when switching from ATI to nVidia the best thing to do is reformat HDD and reinstall the OS
That's horrible advice! All you need is driver cleaner
if ever you switch videocard companies.
BTW........with multiple slots on PCI express motherboards and the ability to have two vid cards working together for faster rate.......willl it be possible to have a high end gaming card in one slot and let's say a Quadro fx 3400 PCIe card in another slot and be able to switch from one card to another electronically without having to remove one card and pop in anotther?
Bah! Can't help you there.
...RAM increase is neccessary...
Then go with it...