If by "powerful" you mean loudness, the only adjustment would be volume. I believe the output between the standard and premium is pretty close. The 328 also has a small volume to fill. Manufactures increase the number of speakers rather than more powerful amps to obtain greater loudness. You may want to make sure surround sound is on.Many younger owners raised on bass heavy music have supplemented with separate subwoofer. For improve sound quality you may want to check out these posts.
http://x3.xbimmers.com/forums/showth...=premium+sound-Newest setting are towards the bottom of thread.
http://x3.xbimmers.com/forums/showthread.php?t=1041459