Best sounding mufflers on stock 318

If you are not going to run tailpipes, it's going to be a LOT louder. So you have to adjust what you are listening to. Just about any muffler without tailpipes is going to give you the deep aggressive tone you are probably looking for. The DynoMax Ultra Flow and the Pypes Race Pro are literally identical mufflers except DM makes an aluminized and Stainless version where Pypes is stainless. Both these mufflers will be very tame except at WOT. Both will yield some drone at certain cruising RPM levels.

The DM superTurbo is a much quieter muffler and will yield little or no drone but still a good choice if that's what you want. The down side of this muffler is that it is a crimped case muffler. Over time, crimped mufflers tend to develop leaks whereas the welded case muffler last longer. Soon Pypes will be releasing a welded case muffler with the same attributes as the Super Turbo but in stainless and with a lifetime warranty.

Also, cammed motors are going to have a very different sound.

For a stock 318, and with wanting a deep aggressive sound, I'd go with a chambered muffler like the Pypes Street Pro or a Flowmaster 40 series.