In my experience, the "Auto Off" feature on subs has been spotty at best. Consequently, my subs have been staying on 24/7.
Circuit City (via Amazon) is selling the Monster PowerCenter 775G for $16 shipped (MSRP $70).
I decided to order one, and just hooked it up with my Denon AVR-x4000 plugged into the control outlet and both of the subs plugged into the controlled (switched) outlets. Works perfect in my setup!
There are three controlled outlets, three "always on" outlets and the control outlet. Only one "always on" outlet has clearance for a wall wort without blocking another outlet.
Also 2160 Joules surge protection and $400,000 warranty, though I don't know if those warranties mean much.
http://www.amazon.com/gp/product/B004H1PV4S/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1