Should be a good little budget gamer for the money. You should get good frame rates at 1080p with the HD 7790 if you don't try for ultra settings in the most graphically intensive games. If you game at 1600x900 or less, you can crank up the settings more.
I've never heard of CSX memory, so I can't comment on it. But always buy your memory in matched pairs if you are populating 2 slots, or sets of 4 if populating 4 slots. Dual channel requires the memory be identically matched for trouble-free operation.