If you are unhappy with the 2700k, don't expect any significant changes when upgrading to something like the 3770, they have the same stock frequency, same turbo speed, same number of cores, and same amount of L2 and L3 caches. The main advantage of the 3770k is better power consumption.
A common mistake in FSX, is believing that upgrading the processor would automatically give better results. Yes, if you were upgrading from a much worse CPU, but not in your case, where you existing CPU is already a very good one.
Best spending your money in a graphic card with lots of RAM (like 3GB), if you don't have it yet, and more important of all, purchase add-ons that are known for being optimized, and stay away with products with lots of FS9 code inside.
If you are not happy with performances in FSX, the problem is not likely the CPU, but more the overall system (difficult to say without knowing your specs), the add-ons used, and your settings of course.
