Your posts are horribly hard to read but I'll do my best trying to understand them...

1) New hard disk. A WD Caviar black or faster would be a good fit. Your IDE drive is probably horribly fragmented due to the lack of space.
2) Are you using the latest nvidia drivers? Or whatever was in the asus cd?
3) If SC2 made near full use of 6GB of RAM, you'd hear nonstop whining from players over it being a memory hog. Most gaming rigs barely use 4GB at most.
4) The GTX 480 is known to be both very powerful AND very hot.
5) SC2 is designed for dual core CPUs and thus wouldn't use the i7 975 to its fullest.
6) The Rampage 2 extreme supports SLI too, but I don't think you should add another GTX 480, the power supply will be really strained with that inside.

IMO, that's 7900 bucks poorly spent, you should've gotten a GTX 480 with a better cooler (hell, you could even buy another card for SLI) rather than spend on the i7 extreme that you don't even know how to make use of to its fullest.

My suggestion:
-Sell the i7 975 and replace it with an i7 930. You'd probably pocket almost RM2000 for that.
-Use the extra money to get a quality 1080p monitor (such as those Dell Ultrasharps) and a real hard drive.
-No need to upgrade your graphics performance, it's not like you can see 90fps on a 60fps monitor anyway.