how to get the 1gb gfx card in the 2.3ghz macbook pro model

Hello all, i am looking to get a macbook pro with the GT 650M 1gb graphics card, i don't even know why they offer the 512mb card on the 15 inch 2.3 ghz model as 512mb vram is useless nowadays for most games. But the rest of the specs on the 2.3ghz model are fine all that is needed is to upgrade its graphics card ram to the 1gb model but that would require shifting to the 2.6ghz model (if purchasing online?) with a huge jump in price for unneeded specs. Is there any way apple might let you up the graphics card in the 2.3ghz macbook model to 1gb? not for free clearly but dont want the additional price of the unneeded extra 4 gig of ram higher capacity HDD and 2.6 ghz cpu