I would definitely suggest a different motherboard. Many people like ASUS and I have nothing bad to say about them.
Go with 8GB RAM. 16GB really is not needed for gaming. 8GB can be found for 40-50$.
So does your budget include purchasing Photoshop?
Well it looks like you still have some wiggle room in your budget. You may want to consider bumping the GPU up to a GTX 570 or looking into an SSD as a boot drive. This will make your build feel so much faster and can be the best single upgrade anybody can do.