I cut the muffler and resonator off of mine and welded in strait pipe. Its loud as hell when the engine is cold, very raspy too when cold. It smooths out as the motor gets warm. I really didn't notice too much as far as a power gain though. I think the cat is probably the most restrictive part in the exhaust system.
I have the 1st resonator removed( under the car), and pipe welded back in. Cost me $50 at a local shop. Before having it done my ATX could not turn them over, that day it could. After installing an SVT snorkel 2 weeks ago the sound of the exhaust changed, it is a little more quite than before the snorkel. I have been driving the car with the exhaust like this for over a year now, no complaints. When all the testing on the high flow cats, and cat-backs is done I'll be switching it out.