Never heard of SDmotorworks.com. The exhaust can be purchased for around that price from reputable vendors.
Acoustics in the hatch & the sedan are different. I'm not sure whether you have a hatch or a sedan. It is rather difficult to find an exhaust for the hatchback that will sound "mellow". The Q300 on the hatchback drones a lot more than on a sedan. If you can, try to go to a local meet & hear the exhaust in person. Shouldn't be too hard in Philly.