I would definitely recommend 8gB of RAM (using 9gB myself and use up to 80% of it with wow only open, Core i7 system). And get a graphics card with the most GRAM you can afford (again using a 1GB GTX280 myself). And use XPx64, ive used XP64 and Vista64, and with Vista my latency goes up by 100-150ms, even when only playing 1 character (worse if my virus/firewall is running) - its almost always in the red on 1 char in Dalaran, compared to low yellows under XP64.