If I presume correct, the HD 7600m is a dedicated graphics card, so increasing the RAM will not help that as it will use its own video memory. However, the Intel HD graphics essentially steals/reserves memory from your RAM so it can be used as video memory when needed, it's hard to say how much without knowing the exactly Intel HD graphics chip, but increasing your RAM to 8GB's will see a noticeable improvement in multitasking and perhaps a slight improvement in games due to other programs being able freely use the extra RAM, but you will not see a huge difference.