Nothing wrong with your 609. Most 5.1 speakers are not designed for 2 channel music.
I had the same problem as you do before.
During movie/concert playback, the bass is produced by subwoofer. But when you listen to 2 channel music, the sound comes from your 2 front speakers (unless you set to other music mode using other speakers and subwoofer). You may found the small front speakers are too weak in producing good bass needed for music and the sound is too flat.
For long run, I suggest you upgrade your FRONT speakers.