Should I use Win64 with new build?

Okay.. so I'm slowy getting the funds together to purchase my upgrade (almost a new build).

I'm going for 2x GTX260 Black Edition in SLI (with the Accelero Xtreme on them both), The best AMD Phenom II AM2 processor I can get (limited to 95W thanks to my motherboard) with the CoolIT Freezone Elite cooling it (first time using something that can deliver below-ambient temperatures!) and then a new sound card and other things..

Because I'm using XP 32-bit at the moment (current build), I'm limited to 3.5GB RAM. I've read this should be 4GB, but I'm yet to ever see this on any of my computers using XP. I have 3GB 800MHz RAM installed, but two 8600GTS's in SLI which both have 512MB VRAM on them so my computer can only makes use of 2.5GB RAM (3.5GB limit take away the VRAM).

Because of this.. if I update my computer and use two graphics cards with 896MB VRAM on each (1.75GB together) will my limit go from 3.5GB right down to 1.75GB for my system RAM if I keep using 32-bit OS!?

Should I install Windows 64-bit so I can have my 1.75GB VRAM, and then also upgrade to 4GB or 8GB 1066MHz system RAM?

Any advice or information would be great.
I can't wait to upgrade my system, it'll easily be the most powerful computer I've ever built (or even thought of building lol).

Thanks,
Ace.

I thought about the GTX275s but I really wanted the Accelero Xtreme cooler instead of the noisy stock cooler. I've been told I can't install the Accelero Xtreme on the 275s?

Also, why not XP 64-bit?
I personally HATE Vista, and I can't get Windows 7 yet can I?

Cheers.

Hmm, I did think about the driver support and that is obviously a must. Maybe it is the time for me to ignore all the *** I hate about it and get Vista64 .

Also.. I have several trade accounts with large component suppliers so cost isn't an issue, I can get most items a good 20-30% cheaper than RRP.

I've just been reading up and on a couple of forums now people have said the 275 isn't really worth an upgrade from a 260 core or black edition.. and remembering I'm currently using two 8600GTS cards two 260's would easily do all I need them to.

So maybe if I just sort myself with Vista64 everything will be okay lol.