Well, I've heard the Magnaflow muffler sounds fairly good - only problem with that system is that it includes another set of midpipes with a resonator.
Most who add a performance muffler also do a resonator delete to make the sound even better. Even the BMW Perfomance Exhaust includes midpipes WITOUT a resonator.
Seeing as you already have a resonator in your factory system, if you want to keep one - you'd be better off just buying the appropriate Magnaflow muffler only and custom welding it onto your existing pipe, instead of paying for yet another resonator.
There are plenty of threads showing how the muffler alone installs if you do a search...
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