I'm looking to put a cat-back system on my grand prix by next summer (as soon as i get the money). I've been looking at Dynomax's with their ultraflo mufflers, magnaflow's, slp's. I'm having difficulty deciding what to go for since dynomax's r aroudn 300 bucks cheaper than magnaflow's and slp is right in the middle. i thought at first the dynomax ones were not stainless steel making them cheaper but they are stainless steel. i think i can throw slp out of the mix because they don't produce the sound I'm looking for. I'd like the sound to be a deep rumble. And also i want the system to pass emissions (I'm in connecticut if that matters) so I don't have to take it off and put the stock back on just for emission tests. So can I have your thoughts on what I should go for? Is magnaflow really worth the extra 300 bucks compared to dynomax?