1600MHz memory is the sweet spot for price/performance but that performance will NOT be shown in games. Games take little to no advantage of faster memory be it 1600MHz or 2500MHz. Gaming memory is a marketing gimmick because faster memory doesn't effect gaming unless you are running another program that is memory intensive while gaming.
Compression/decompression takes the best performance increase of any program except maybe rendering when you have faster RAM and most other applications improve slightly but frames per second in gaming does not get improved.
1600MHz is usually the best way to go but don't expect a direct performance increase in games from it.