Affordable subwoofer for music cont'd

Oh stupid webpage, this forum doesn't cache your pending response so when you click on a link, then go back, what you've typed isn't saved. Crap. No offense, but this is the first forum I've encountered in a while that doesn't have this feature. :(

Anyway, to answer a few questions.
Bottom line, my budget is roughly $200 for a sub. I spent $200 on my CD player, $200 on my receiver, and about $200 on my speakers. I spent $35 on cables. I would love to have a larger budget that would get me into NAD Silver stuff and some Paradigm Reference Studio 80's, but it's just not in the cards. I don't have a "real" job yet. So, recommendations above $300 don't mean much to me as I simply cannot afford them.
That being said, the Infinity is out of my price range, though I'll check out the Pinnacle, NHT and Aperion Audio.
For what it's worth, the K-9 is a sealed sub, the only sealed sub of the three I listed. That's why it doesn't play as low, or have/require as much power, but also why I speculate that it will be able to keep up better with the music.
If anyone has any opinions comparing these subs that I listed, I would really appreciate it as they are the only subs I have to choose from right now. And hey, if I don't like one, I can always sell it and buy another one at a small loss (the beauty of buying decent stuff).

Blkadr, Your response reminds me of a parallel situation with cars. I love Subaru's. I drive a '97 Impreza Outback Sport. Decent car. I'd love to be driving a 2005 Impreza Sti. Too bad it costs 3x as much, and I'm still paying the '97 off. Sometimes we have to sacrifice what we want for what we can afford.
And anyway, a stereo isn't "my all" in life. I also DH/freeride mountain bike, hike/backpack, rock and mountain climb, and drive my car on gravel roads very fast for fun. These are also money-gobbling pursuits. If I only sat at home and listened to music and watched movies, I'd have nicer stuff. Fortunately (or unfortunately, depending on your outlook) I'm a very active person, and only a fraction of my play money can go to a stereo. So, I buy as high end of audio as I can afford and appreciate after a long night in a storm or after a hard mountain bike ride.
I have checked out those Dayton Audio DIY subs on ebaY. I looked them up on Parts Express, and they were out of my price range new. I'll keep an eye on ebaY for them, or maybe parts, and build an enclosure myself I am just afraid of getting the right frequency response out of a particular driver/amp/sealed box combo. I have modeling programs that you can input T/S parameters into, and get a response graph, and I could use a woofer's parameters combined with the box size to get what I desire. I would just need to make sure that the amp was up to par as well. For that I would like an on/off switch, phase adjustment, LP crossover and a single RCA input jack. I can't think of anything else I'd want for music, though it'll probably have speaker-level inputs, outputs, and RCA outputs as well.
The main problem with all of this though is that even if I get the parameters right, the box right, etc etc... it could still be a mediocre sounding sub that cost just as much as a reputable manufacturer's offering that DOES sound good. So, I'd like to try DIY, but I'm just skeptical that it will turn out as well as something "engineered." I'm not afraid, or even uneducated, just wary.
Anyway, I'm rambling on, so any more advice on the subs I have available to me would be great, and I'll check out Dayton.

Accorddude,
Thanks for the opinion. I will more seriously consider the DefTech (I think it's mostly between the DefTech and the M&K, though I was leaning toward the M&K because I don't have much music that has bass below 35Hz). I am also looking for a deal on a Dayton Titanic 10, but it'll have to be under $200 shipped as well, or I just can't afford it. They do look cool though.

I ride a custom SC Bullit around Bellingham and on the North Shore, as well as Whistler and Hemlock in the summer. I climb around Bellingham, though I get to start that up again this summer after a two year hiatus due to a broken toe, then as soon as that healed, a broken wrist. Never done much more than sport, but I enjoy that enough! I boulder a lot too because climbing partners can be hard to find.

Well, the M&K was sold out from under me, and the seller of the ProSub 80 backed out on selling once I confirmed the desire to buy, so I'm back to square one. Suck.
I'll continue to watch the auctions for Daytons Titanic MKIII's as well as the Pinnacle Baby Boomer, Aperion Audio S-8APR and anything else sealed and small. There can't be much demand for small sealed in home audio because everyone wants deep bass for movies, right? I hope not...