Wich onde is better??

Hi all! I wanna build a gaming pc but I'm having a lot of doubts in choosing the graphic card and the processor. I dont know much about on-board and off-board cards and need to know: Are all VGAs for notebooks on-board? If they are, it means that if the graphic card gets obsolete in the future, I wont be able to replace it?
I was at Alienware site (cause I live in Brazil and that's the only website I know that ships their PC here) and got stuck between choosing a Core 2 Duo T5600 1.83GHz with a 256MB ATI Mobility Radeon X1900 or a AMD Turion 64 Mobile ML34 1.8GHz with a Dual 256MB NVidia GeForce Go 7900 GS - SLI Enabled.
I'm pending more for the core 2 duo side, cause It's a lot cheaper for me (as US$1.00 = R$2.15-> our "coin" and the shipping is US$250,00!!), but i need to know if that's a bad deal or not... That's why i need your help!
Also: does anyone knows more websites that ships their products to other countries??? Thanx!
Obs.: I forgot to tell that i want a gaming notebook.

This is the new upgradable video for laptops. Nvida anyway.

http://www.nvidia.com/page/mxm.html

This laptop has it.

http://usa.asus.com/products4.aspx [...] odelmenu=1

Want one? PM me.