First off, Welcome to the Jeep Forum here on the KK side of life.
I really think that you can find all the power you may need under your right foot. Just smash that little pedal down hard and go. You could also if when needed push the "Tow/Haul" button and it will alter your shifting points of the transmission, which may give you what you are looking for.
Now with the above be said, there is always the usual suspect parts you could throw at the Jeep, like the KN air filter, aftermarket free flow exhaust or computer programmer.
KN filter over the years has been shown in many cases not to provide enough filtering of dirt. Also replacement filters have evolved enough that the difference in air flow maybe minimal at best.
As for the computer programmer, I have heard that it is a short term effect. That eventually the factory program will over come the new program and you will be back to stock. Don't know if that is fact or fiction, but it is also difficult to find a tuner for the Liberty KK.
Now for the exhaust, I have always believed that the only thing the aftermarket exhaust will do is add noise. And that an aftermarket exhaust offers no real benifit other than to free up the flow of pressure. However, I did install the JBA exhaust and my only expectations were more noise and a bright stainless exhaust tip. But for some reason my in town mileage has gone up 3 MPG and acceleration has improved both from a dead standstill and in on line acceleration IE: passing. The MPG increase is based off of readings from my ScanGauge, the acceleration is a pure "Seat of the Pants" feel. Even my wife has noticed the acceleration difference. So for $149 the exhaust was the best bang for the buck I have ever purchased for any vehicle
I am sure some others will chime in and either dispute or agree with what I have said.
"If you have a difficult job to do....Give it to a lazy man....He'll find the easy way to do it."