It wouldn't really give you better performance IMO, you don't even really need 8GB. At the same speed, look for lower timing RAM sticks, and rather use extra money you would have paid for another 4GB, and get faster 4GB RAM. =)
I would say 8GB is nice to have, but definitely not necessary. For gaming 4GB is usually plenty but with video editing the extra memory should come in handy. Memory is rather inexpensive nowadays, the kit you picked out is fine. So either go with that kit, or you can get one of the 8GB 1600mhz CAS 9 kits rated at 1.5v (they are all the same, just rebranding and different heatspreader) if you want to go with 8gb.
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