Toshiba a500 laptop

Hi everyone! i am in the market to get a new laptop and i had seen this laptop from toshiba, the a500 series laptops, i'm planning to get a customized one from toshiba so that i could choose which parts i want and which one's i don't want. anyway my dilemma here is that it offers Ram in 2gb, 3gb and 4gb. and i want to know is that does it support dual channel memory? it uses ddr3 ram to run. and what would be the better choice if i'm planning to run windows 7 here