What is my best subwoofer option?

Here's my situation:

I have a Yamaha RX-2700 receiver.

A friend gave me a couple problem subs. One was a Velodyne HGS10BG. Amp worked for a couple minutes after being turned on, then began crackling and stayed crackling. I replaced the caps but it didn't help and now the amp is basically dead.

The other is a significantly bigger Velodyne but I don't see model # anywhere on it. Amp is also dead. This one also now has a ripped cone (actually the foam outer ring).

Since neither have a working amp, what I am currently doing is running from the Sub Out of the Yamaha into an input on an old Onkyo stereo receiver, and from the regular speaker outs of that directly to the speaker of the sub (the smaller Velodyne since the big one is blown).

I saw the sale on the Epik Legend but was gutted when they sold out just a couple hours before I went to place my order.

So my question is, what should I do? How much difference would I see from my current jury-rigged setup to something like the Polk PSW505, currently at Amazon for $189, and in which direction? How big is the difference from the Polk to the Legend, which would be something like $650 with shipping whenever it comes back in stock (as opposed to $380 at the sale price with Discover Card promotion -- yep, I'm still just sick I missed it)? I see there is also the PA-150 at $425, the HSU STF-2 at $375.

For what it's worth, the front three speakers are Canton Karat CM4s. The surrounds are just the satellites that came with my initial HTIB, and are the only remaining elements of that HTIB that weren't replaced by donations from my friend.

I'd say $400 is my limit and I'd like to keep it well under unless this is something a layman would really hear a big difference in, justifying significantly more cost.
Edited by curttard - 12/5/12 at 11:42pm

How much is the sound of my Velodyne compromised by being powered by a cheap stereo receiver rather than its own amp?

Would the Polk be a step up from my current jury-rigged setup, or a step down?

Would the average person notice a significant difference between the Polk and the PA-150?

How much better is the Epik Legend than the PA-150? Would the average person notice a significant difference?

I've always been a bit behind on the audio, I had only a $300 HTIB until my friend began donating his older gear to me.

P.S. I'm not sure about the $350 PA-150, that's from Acoustic Sound Design and I'm a little skeptical of them. Their policies suck -- only a 7 day return policy, and then only for credit; 4% processing fee for a cancelled order even if the item hasn't shipped yet -- and all the positive reviews on resellerratings.com sound like they're written by the same person, and each positive reviewer has only reviewed them and no other store; and the bad reviews are really bad.
Edited by curttard - 12/6/12 at 10:09am

Yeah, I've been doing loads of reading here, just trying to figure out what would be my best bang for buck without making me wish, a year or two from now, that I'd spent a bit more for something significantly better, while still taking into account that I don't have a $20,000 system and am not obsessed with shaking the house.

Not sure on room dimensions exactly, will measure tonight. Will be moving next year, though, and don't know if space will be bigger or smaller.

Concerned with movies and games, music is distant second.

Contenders and best prices I've found:

• Polk PSW505 @ 190
• BiC F12 @ < 200
• PA-120 @ 220-230
• BiC VK-12 @ 285
• Klipsch RW-12d @ 300 if another Newegg deal pops up
• BiC PL-200 @ < $330, not sure on what actual price would be
• PA-150 @ 350

Yeah, I guess what I mean by "bang for the buck" is "would I notice a very appreciable (and of course positive) difference from one to the other without directly A/Bing them one after the other?"

I think it's actually more likely that I'll have a smaller room when we move.

Well, I'm going to have to hope that isn't true

I wasn't itching to upgrade back when the bigger Velodyne still worked, before it got ripped up. I assume any of those above with an actual working amp should outperform it?