I do have to correct you a bit.
Being "large address aware" allows using up to 3gb and works even in 32bit OS.
C6 is not "large address aware" and generally becomes unstable approaching 1.6gb usage. As far as I can tell some garbage collection is started around that level of usage and it never finishes. In very complex renders, using multiple threads, I've had memory allocation errors when getting near the 1.6gb usage.
Using a 64bit os and multiple core CPU's has an advantage when using your computer for multiple tasks but you should use some kind of small render farm (even 1 additional computer is a bonus) for all rendering to continue using your main computer even when rendering.