I think he's just confused about the sound emanating from the engine vs the exhaust. The sound you're referring to comes more from the exhaust tuning, not the engine layout. For example, Nissan used basically the same exact 3.5L v6 in their 350z sports car and their Maxima, but the Maxima's exhaust is tuned to be sedan like quiet, whereas the Z is tuned to sound aggressive at low revs to make that growl you always hear when they drive by.
Similarly, the Subaru WRX's exhaust is tuned to sound more aggressive than say, their Legacy sedan. With the flat 4 engine in the Legacy, you don't notice that same burble you do when a WRX drives by right? So you are confusing an engine type with an exhaust tune. If you like a more aggressive exhaust tune, get a different exhaust for your Boxster.
The early Boxsters in particular (97-02), had extremely wimpy sounding exhaust tuning (unless you ordered their PSE). After 03, Porsche started tuning their exhausts to sound a little more sportscarzy. In my opinion, Porsche should've just supplied every car standard with their PSE system...I mean, why should you have to pay extra for the car to sound like a sports car?...Nissan doesn't charge extra for their nice sounding Z exhaust...it comes standard with the sports car, but no...Porsche needs to upcharge their customers.
I also hated the sedate sound from my 01's basic muffler, and my wife hated the drone from my pal's GHL, so I compromised and put on a Dansk exhaust that wasn't as loud as the GHL, but still had a little more bark without any drone that I could detect....
Check out the goofy video I took:
Dansk Exhaust Video