The subwoofer is, IMO, the one place in a surround sound system where you should really never skimp. Reproducing deep bass is difficult, and there's just no getting around physics. It takes what it takes, and it isn't cheap.
My advice: if you can't afford around $350 for a subwoofer, go as inexpensive as you possibly can so that you can save up that much quicker, and upgrade to a $350+ subwoofer in the future. I consider something like the HSU STF-2 or BIC PL-200 to be the bare minimum for genuinely good bass. And I consider around the $550 mark with the HSU VTF-2 MK4 or Outlaw Audio LFM-1 Plus or Rythmik FV12 (if it ever comes back in stock) to be the least expensive subwoofers capable of "doing it all", by which I mean they can genuinely play down to 20Hz, they can play accurately and linearly, and they can play loud without distortion.
Dropping from the $550 subs to the $350 subs forces you to lose a little bit of extension (around 25Hz instead of 20Hz) and some output. But at least you can still get high quality bass that is accurate and linear, and still quite loud without distortion.
Dropping below $350 tends to mean some pretty big sacrifices though. You start to really obviously lose extension (serious roll off in the 30Hz range insead of 25Hz, and 20Hz is completely out of reach). You start to give up linearity and accuracy. And you start to get some pretty serious distortion, especially at louder levels. It doesn't have to be terrible, but there are almost always some pretty obvious compromises being made.
So I suggest going as cheap as you can if you can't afford $350. I tend to recommend the
Onkyo SKW204 . It's actually a surprisingly good little subwoofer - always manages to bring a smile to my face
At $90 from accessories4less, it's a great deal. But they're sold out at the moment I'm writing this. A4L tends to get stock of the SKW204 from time to time. They always sell out quickly. So if you decide to go with this Onkyo sub, just keep an eye on accessories4less every day, and grab a unit as soon as it's available in stock!
You can find the SKW204 for around $145 at Amazon and the like, but at that price, it's not as good of a deal. What makes the SKW204 make sense to me as a recommendation is being able to spend under $100 for a sub that, while obviously not as good as the $350 or especially the $550 subs that I've mentioned, it's still pretty good, and will at least deliver fairly accurate, punchy bass that nicely fills in the low end for movies and music. By spending under $100, you allow yourself to save up in order to afford one of those $550 subs. It's a very small bite out of your wallet, so it's easy to accept any short-comings, and you can easily make your money back if you decide to sell the SKW204 when you upgrade. If you spend closer to $200 right away, you don't really get any sonic benefits - those subs are still heavily compromised and obviously not as good as the $350 or $550 subs. But with $200 gone, it's harder to accept the short-comings, and you're less likely to get that full amount back if you sell it.
So, that's my advice, in any event
