My first post here & glad to be part of the community! I'm sure the topic has been beat to death, but here's my .02
Being the cheapskate that I am, I did some research and found the cheapest system that would help the most. I had a hard time finding Dyno sheets on 3.7L applications but Magnaflow does have
info. Magnaflow was beyond my budget, but Dynomax Ultra Flo mufflers are basically a lesser quality magnaflow universal muffler, so I'm assuming the performance gains are the same. I found the cheapest dynomax system
here and dynomax is currently running a $75 rebate, so my cat-back came out to less than $150.
It sounds good enough for my needs. Not too much interior noise and not high-pitched. Of course it'll never have a nice, deep V-8 sound, but I'm over it. There is a noticeable increase in power and I consistently have a little better gas mileage as well.
note: some others have said that performance exhaust rob you of low-end torque. I haven't noticed a drop-off in torque when driving, but the Magnaflow dyno chart only shows 4500 RPM & up, so they could be hiding something.