I think the PE exhaust is basically an incredibly well engineered muffler delete. It's nearly as loud as one but with a much more refined noise. It is absolutely NOT daily driveable because even with the windows up and music playing, the drone overpowers the cabin and will rattle trim pieces which never rattled before. But my god, the noise is makes at WOT above 4k (especially in tunnels) will paint a smile on your face and cut your avg MPG's in half. Before you slap on a new muffler, run AA headers + PE muffler for a little just to experience that noise
AA muffler with headers is more muted than the PE. It will still have SOME drone but nothing that you can't live with. WOT still makes a pretty noise above 4K but not the banshee wail of the PE.
Stock 128i exhaust with headers apparently still sounds stock.
135i exhaust and headers doesn't sound bad at all. Almost no drone. Can't hear it with the windows up and music playing. But WOT still plays a racey, slightly raspy BMW note.
Now I'm just curious how AA headers + magnaflow exhaust sounds. Maybe bimmerbob can chime in.