Memory Addressing/Which Vista Ultimate?

[ChromWolf]

I'm building a new gaming rig. It'll be one of those "I only get the best" rigs, and certainly with the intent to brag (I can at least be honest about it, lol).

I've decided I like Vista. I've really only recently gotten into it and have been a long time "Vista hater", but it was purely out of not having played with it and listening to what others were saying--I can admit that too. I've played with it at last, and... well, I want the pretty! So, I think I'm okay to not have to ask whether I should go with Vista or not. That makes my question more of a technical one than aesthetics...

The idea is to get a couple BIIIG video cards (potentially twin 9800 GX2's) to SLI together (I'm not sure if I want to go with tri-SLI just yet, I think that's for another thread). I knew the system would certainly have 4 GB of memory, and figured Vista Ultimate would be the pretty (and power) I'm looking for. But then I'd heard that there's something with Vista where it has to address the memory for the video card(s) into the system memory as well... Such that essentially, if you have a total video memory of say, 2 GB, you effectively "loose" that much of your system memory. Is this true? ...How would this affect a tri-SLI rig, then?

The next question then is, for an "uber" gaming rig, is the 4 GB enough or will I need something more like 8 GB, and therefore Vista Ultimate 64?

I'll mostly be doing WoW (occasionally other games, definitely Diablo III once it's out for example), and then a fair amount of mid-size apps (i.e. more than just web-browsing and checking e-mail, but no video or 3D-rendering), in case it's more a "what will you be doing with it" question.

Is what I heard about Vista's memory handling for video cards true? If so, will my 2 GB (remaining from the 4 GB system mem) be enough for everything else, or go 8 GB and Vista 64? ...What other hardware compatibility problems might I have, assuming I go with (all but the) newest hardware available?

[shadowpr]

Get 4gb and vista 64.

[Kuch]

Ditto what Shadow said. I'd actually go with Vista Home Premuim 64 and 4gb RAM.