Minecraft Server Lag

[Edge100x]

The speed of the processor is not your limiting factor here, no. Your issue is more fundamental than that, as a software problem, and your processor is already just about the fastest available.

If you only use one core of your E5-1660 (which seems to be the case), then you're going to be running at the maximum turbo speed of 3.9ghz, which is pretty much unbeatable. You may be able to find a same-generation processor that turbos to 0.1ghz higher, but that is a tiny amount and would not be enough to save you from the problem you described.