I've not installed any 2.5" exhaust yet, but have had it on my list to try after fixing everything else on the jeep first.
There is one on Amazon for a really low price:
Two reviews from CRD owners give it 5 stars, although one points out cheap feeling materials, which was expected given the price, but it is 2.5" so might be a way to try it out for less before building a better quality one.
And there is one from Sasquatch at twice the price, no idea on the quality, although the other things I've gotten from Sasquatch have been good (upgraded turbo and battery tray):
To save costs, Jeep equipped the Liberty CRD from the factory with the same small-diameter exhaust system designed for the gasoline engine. This factory system, which necks down to 2", does not flow nearly enough for your turbo diesel engine to perform at its best. Let your engine breath with...
shop.sasquatchparts.com
If you want to build your own Magnaflow system, check the below out for some ideas:
jeep, libety, crd
liberty.eurekaboy.com
Tim