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.
Meant to say "Ideal Budget Subwoofer"
A couple more pretty nice budget subs are Emotiva and Epik which I think are in or close to your range. That's a growing market.
hsu (which i believe also designs or makes outlaw's subs)makes a great product and would be my pick. i also like deftech supercube and the martin logan dynamo, which you can find in your price range.
Hi Mntnman62

I say keep it in the Polk family and get a Polk Audio PSW505 subwoofer.

I got one for my dad's HT set-up and it sounds great in his room and gear. It compared very well to a Velodyne SPL1200 that my uncle had loaned to him before I could get him the PSW505.

The PSW505 he has also has BASH amplification.

Good luck with the search.