Ideal

I presently have a Harman Kardon HK3490 driving a pair of Silverline Audio Minuets and a Polk PSW10 subwoofer in my basement mancave/gym/drum studio. I am in the process of purchasing a micro system for the office and intend on using my existing polk sub with the office micro system (probably the Onkyo CS-445). That means I am in the market for a nicer, yet still budget, subwoofer to complement the HK and Silverlines. When I say budget, I probably don't want to go much more than $350 to $400. I've looked into other Polks, PSW111 (seen it for $150)and PSW110 ($160), and Hsu stf-2 ($350), Def Tech Subpro 60 ($128), Sunfire True Sub Super Jr (a bit pricey), Outlaw LFM-1 (hard to find) and Dayton Audio T103K and Sub-100 ($400 and $130 respectively). I would be grateful to hear what you might suggest, whether you like any of these options and what other options may be out there that I have not considered. I am somewhat reluctant to buy a used subwoofer so new is the preferable approach. I should also point out that the room is approx. 10' x 20' and I have only researched online but have not auditioned any of these yet. Many thanks for your insight and perspective.