I ould also suggest u to get the custom kernel by nAa. It has quite a number of advantages over the stock kernel.
There are no FC s or slow ups in the mobile. The speed will be very good. (Though in new condition... sony's stock UI is also very snappy). what is doesnt improve a lot is its battery life(especially if you use internet all the time). If you are ok with the current battery back up... you would be happier with this one.