Jeep Repair: Power, jeep wrangler, salvage yard

Question
Is there anything I can do to get more power out of my 2000 Jeep Wrangler 4 cyl? If I decide to buy a 6cyl from a salvage yard, will I have to replace the tranny as well?

Answer
There's another guy who's asked some questions about his 4 cyl TJ as well.  You may want to check some of my previously answered questions to see what combination he went with.   

If it's the 2.5L engine then I'm sure there's plenty of aftermarket support out there because the engine's been around for a while.

If it's got the newer 2.4L engine (I think that's 04 and newer) then it's the same engine as found in the turbo neon and pt cruiser.  Can you just imagine a turbo wrangler?  ok, so I'm a little twisted.
Doug