buying just the DSB2 Sub for DSB1 sound bar?

[QueBert]

Had Dish installed yesterday and they're running a free Polk DSB1 Sound Bar offer, it didn't come with the sub though. And the installer said it doesn't, but Dish will sell me it to me for I think be said $300. I'm finding them sold together everywhere else for $300'ish. So no way will I drop that much on just the sub. It doesn't look like anywhere sells the subs by themselves. The installer wasn't too knowledgeable, and the 2 different CS people I spoke to didn't even know about the promo at all, and were unable to help me. I asked if I was suppose to get the sub, and neither had a clue. Since it was free I can't complain much, but it sucks I can't find the sub. Anyone know of a place I can order just the DSB2 sub?