Discusion hardware&software

now i got
soft
skp 6 + new v-ray, win xp 32bit [max use ram for skp is ~1,6]

hard
q9550
4gb
3650

i know i will change 3650 for quadro fx 580,

and the question is

if i change 4gb to 8gb ram + win xp 32 to win xp 64 bit + skp6 to skp7, i will see some difference ?

can skp used more then ~2gb ram in single model [i make arch model with full of trees for example ?