Ideal Budget Subwoofer

[MntnMan62]

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 that 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 another Polk, PSW111 (seen it for $150) and Hsu stf-2 ($350). I would be greatful to hear what you might suggest as to whether the Hsu is that much better than the PSW111 for more than twice the price 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. Many thanks.