Will it make a difference? GPU+RAM Q's

So as you read this please keep in mind that yes I am probably splitting hairs with this question.

As Toms (thankfully) does various CPU and GPU reviews and charts they do, unless specifically noted, tend to run the best available equipment aside from the piece they are testing. Example, if they are testing a 9800gt they will do so with the same platform as they would test a gtx260, that way there are no choke points except for the hardware in question. This gives the clearest most accurate rating for the hardware.

Now, with that in mind I make the assumption that they are more than likely testing with a 64 bit OS, regardless if they are using 4 gig of ram or 6+...

...so, down to the question...

Let's pretend I am using a 32bit system, thus the architecture of the OS is limiting me to 4gig of RAM, including the GPU.

So, if I am using a card with 512ram, then my system would show around 3.5 gig, if I have a video card which is using 1gig of ram, then my system would show around 3 gig.

So, with the above in mind, for someone with a 32bit OS, would there really be a performance gain having say a 250gts with 1gig of ram, vs a 250gts with 512? Since the 1gigGPU will limit the rest of the computer?

Am I completely wrong in my logic here or is there something i don't quite understand (which is highly possible!)

also.. i would have to question the use of SLI and CF if you are running a 32bit os.. if you have 2 video cards with 1 gig of ram each, that only leaves 2 for your machine..


So, in closing, someone smarter than myself please set me strait here..