What sub under a grand?

I also use a Gallo sub but thought I'd get laughed off the site for suggesting it. It replaced a sub that was three times as expensive and within the first five minutes of use I thought it was a much better fit.
My other suggestion would be a James Loudspeaker sub. I owned an EMB-1000 a few years ago and it was fantastic. That sub always comes to mind when the "what piece do you regret selling" thread pops up.

I replaced a REL Storm III with two 12" DIY Rythmik subs and cannot speak highly enough. For the price of the Rel I bought the two kits. And cannot speak highly enough about using two subs vs one.

Start out with one of these pre owned and add another later
the units ship at 103 pounds weight ea and will out music anything listed above I promise.
The real advantage is a smoother in room response and blending your existing speakers by High passing your mains will dramatically clear up your whole system.
JohnnyR
Vandersteen dealer
http://vandersteen.com/products/model-2w-series-subwoofers

I use Rythmik subs and can absolutely second the recommendation, but I'd also think hard about the SVS dual SB-1000 offer. A pair of sealed SVS subs with 12" drivers at $950 is probably a great way to maximize your chances of getting great sound, because A) SVS makes a very highly regarded product and B) dual subs offer a lot of placement flexibility (which really improves your chances of smooth, well integrated bass response).

Good luck

YEs, two good subs are almost always better/easier than one.