The Core 2 Duo T9600 is about the top end of the X38 chipset / PGA478 socket food chain. There are no available CPU upgrades that really make upgrading worthwhile.
The Asus W90Vn uses a MXM video card connector which, in theory, makes it possible to upgrade a video card. In reality it just makes it easier for a repair tech to change out the 9800M GS card if it ever fails. A upgrade card would have the MXM edge connector, but would also probably be shaped differently, have different power and cooling requirements.
To know for sure - I think you'd want to ask the same question in the Asus support forums.