The cheapest full x-pipes have no resonators and are really loud. You have to be young to enjoy one. TopSpeed sells one for $500 on ebay. I bought one and it fits and seems well made, but I am adding four resonators. Resonators are pretty cheap -- about $50 each.
The problem with Turner test pipes is that they eliminate the primary cats that sit right before the rear 02 sensors so the car should not pass readiness inspection during the OBD2 plug in. It will probably still pass a sniffer test because the secondary cats are still there. You could probably add a set of 02 bungs after the secondary cats and extend the 02 wires.
Sosi sells a partial x-pipe that leaves the primary cats in place and eliminates the secondary cats and the stock resonators. The consensus seems to be that the primary cats are the biggest blockage to flow and that the maximum benefit from an x-pipe mod comes from removing them.
It is possible to substitute one pair of high flow cats for the four stock cats. Akra uses 100 cell units, but they won't pass a sniffer test. You need at least 200 cell units to do that and possibly 300 cell units -- I would like to see some data on 200 cell versus 300 cell. High flow metallic core cats range from about $100 each to about $500 each depending on which brand you buy.