I have been missing a subwoofer for my Q acoustics home cinema setup for a few years. The 3060S seems to have decent reviews and RIO is selling it with a pretty good price at the moment. Only white and walnut finish available. It is usually $749 and the next best price seems to be $649 at CHT.
Gumtree.. Yamaha yst-sw90, 120, 150, 160, 200, 305 and probably others, see if you get lucky.
They are old though, so not easy to come by. Great for under a pc desk. I've got a 150 and 120 iirc.. Trying to make myself part with one but not sure
Yamaha subs suck
It's about the form factor.
This form factor most subs suck because the driver has to be small. Q acoustics are turning the unit on the side to counter this, but I suppose the resonance in the box suffers due to the void being smaller. Shrug.
Been looking for a narrow sub. Unfortunately this one is a bit too upmarket for my setup (i.e. wife would kill me). Good deal though.