What is the best upgrade I can do on my SE K800i to get the most out of it?

[cheapkites]

First of all,let XS++3.1 Darwin to upgrade your CID49 to CID52,because than you can do what ever you want and next thing you can update your firmware with this tutorial XS++ 3.1 Guide-Flashing, Customizing, Recovering - Top Sony Forums and another thing - whan you first time connect your phone with XS(in Xs folder you find log) post log here without IMEI number and don't try to update with SEUS,because you get CID53

Nice thread - some good stuff to consider.