I just did this swap to my X9 today actually.
I just changed out the driver to the kd 2.8a driver. I am getting 2.7a on high which was a huge gain over the 1a i was getting with the factory driver. However I am now having other issues. The spring on the new kd driver causes the battery to sit much longer and the tailcap won't even get close to screwing all of the way on :S I've clipped the spring on the driver down a little bit but still have a ways to go before I can get it to fit properly. Ordering flat top cells may help a bit but I am looking for other remedies.
Either way, it looks much brighter and I can't wait to test it out tonight!
If you want info on the driver itself see this thread. Page two is where brted helped me and posted a photo of a similar driver so that you can get an idea of where the points are:
It is quite tricky, the points are so small. I had a friend who is an electrician help me and even he had a tough time soldering the tiny details. I would have taken photos of the process had I seen this thread earlier. Sorry!