An under-appreciated sub is the Martin Logan Depth i (and I assume the Descent would be aswesome as well, though I have not heard one). I have used either a single or a pair of the Depth i in my systems for years. They are very configurable, very musical, and fast, and I never had an issue paring them with any speakers that graced my system, including Eggleston Andras, Klipsch LaScallas, Zu Essence, etc. They also server dual duty for HT.
I'd be lost without at least one!
I'd be lost without at least one!