Tvad, a sub is not necessary with the W/P 7's. The bass is lightening fast, smooth, deep, and as tonally accurate as any speaker I have ever listened to. The addition of a properly set up sub, the watchdog in my case, appears to augment the entire range of sound, not only the bass. It is a subtle difference but one that can be heard and felt. It is not necessarily more bottom end, but the sub captures the ambient bass line in singers voices, strings, instruments, etc. for a fuller smoother all around presentation. It is not that the W/P 7 in particular is missing anything, any speaker system will benefit from this. I auditioned this set up in the same room with the mega dollar X-1's and I preferred the WP 7, watchdog combo. The X1's needed a larger room to sound their best.