It really depends on what you're doing. 8GB is more than enough for almost anything. Media editing, RAM disks, and running multiple Virtual Machines at the same time are just about the only reasons for more than 8GB.
Also, 1600 is the sweet spot and there'll be virtually no real world gains from anything faster. RAM related benchmarks will show the difference and it will help with RAM disk speed, but you'll never "feel" the difference otherwise.