Just to clarify about the GPU, in the G6 you can choose to use ONLY the 7670m, and in that case, in will be exactly similar in gaming performance to the g4 lappy.
However, if you Crossfire the 7670m with 7640G, then in most games you will get BETTER gaming performance in MOST games because it combines the power of them both In earlier times there used to be certain issues with Crossfire mode, but with the latest AMD drivers (catalyst v12.10 and above) and the latest HP BIOS update, these seem to have become very rare.
Also, for gaming, image editing and coding, a 15.6" screen is DEFINITELY better that a small 14" one!!
A 500GB HDD these days is also quite small....in will get filled in a few months, I recommend a minimum of 750GB. On top of that, 6GB RAM, is definitely required when doing very intensive tasks like Photoshopping.
The only weak point is the A8 processor in the G6, which is a bit slow than the Intel chips in certain single threaded apps, but most apps nowadays are multi-core optimized (video and image editing and program code compiling are highly multithreaded so don't worry), and you will anyway NOT MAKEOUT THE DIFFERENCE between a A8 and i5 in most daily activities. In the future, when more software supports OpenCL acceleration, the A8 chip will perform even better
So all in all, for your needs, I highly recommend the G6-2010AX for your needs. And on top of that, its 4500K cheaper!!! Who cares if its 300grams lighter....your a man not a girl who needs flimsy light laptops!!