1. Technically no, If you PhotoShop like made, mucho amounts of RAM is something to consider.
2. Those are RAM timings. Apparently, AMD processors don't like RAM faster than 1333 since it can cause damage to its memory controller. DDR3 RAM at 1333Mhz with timings of 7-7-7-21 is the best way to go since tight RAM timings help performance.
3. I've seen that with my motherboard, I have an ASUS madreboard too. It's compatible for 8 gigs of RAM, but there are no qualified vendors for 1333 RAM for 8 gigs, but there are some for 6 gigs, which makes no sense since I don't have a triple channel config. Most likely, if you madreboard can handle 16 gigs, it should and can.
4. DDR3 RAM right now is uber cheap!

From newegg, I'd go for 1333Mhz DDR3 RAM, with a CAS latency of 7, and the best rated by the newegg reviews of customers.
Since DDR3 RAM is so cheap, it makes my 4 gig kit that was a 100 dollars a year ago less than 50 and icky....