I installed a set of the Tubbies on my buddy's Tige boat. They are actually pretty impressive, and quite affordable.
For a Jeep, I would not really recommend them unless your Jeep spends most of its time on the beach. They are pretty big to keep in a DD Jeep. I have seen some people on the forums that run them, I just think they take up too much room to mount to a Jeep rollbar.
As far as performance, they are pretty sweet for the money.
You will need to send a good amount of power to them.