In my opinion it sounds like you should look for another bike. Although I love my XT
, it is no speed demon. I like to think of the XT as a Willys jeep; nearly unstoppable and can go just about anywhere, but has it's limitations, speed being the primary limitation.
I doubt that there is a bike that will fit your desires, fast on road and killer off-road. Determine your road/off-road mix and what compromises you will accept. My suggestions (speed being a major consideration), from mostly street/speed to dirt worthyness would be DL650, KLR650, DR650, DRZ400. Although the 225 and 250 can run 70 mph, most will agree that the bikes are not terribly happy about it.
That being said, I really like how I must take it a little slower on the XT. Just read about Nutzky's get-off at 70 mph. He did not enjoy it.
If your off road will not be much more than graded roads and forest roads, look into the DL650.