im in need of some help.. (1 Viewer)

right now i have a technics sb w500 hooked up to a technics sa ax920....if i turn the dedicated sub knob all the way up i get this annoying rattle....its just not bumping hard enough for me....i found a kenwood sw15ht for 35 bucks....is it worth the 35 dollars? will it bump harder than the w500?

Both are passive subs powered by an amp channel in the receiver so neither are going to give you a lot of bump. Is the Kenwood worth the $35? I don't know. How much is $35 worth to you? To me, it's a wasted transaction because I know it wouldn't satisfy my bass needs. If you think there is a chance that it will improve your system and you can afford the risk, then buy it. I can find very little information on it.
If you want some good bass, then increase your budget and we can get serious. I can help you with subwoofer selections from $120 to $12,000.

so its prolly not gunna be a big improvement...i mean there is alot of bass coming out of my system but im the type of person that likes to push the envelope....right now i have my technics ax 920 with a set of technics lx70 3 way speakers and a set of jbl g300 3 way speakers along with a set of technics surround speakers and a technics center channel speaker...there is enough bass coming from it to vibrate the springs inside my mattress and vibrate the walls downstairs on the other side of the house...i was actually thinking about buying some kickers (car sub woofer) from a guy off of craigslist and putting it in a sub box and hooking it too my receiver...is that possible?

Possible - Yes. Performance improvement - maybe. Potential to blow up your entire system - definitely.
First, Stillwater Designs makes some very, very good speakers but not many perform well in home applications. Some of the newer ones do but they have had one of my favorite transducer engineers working there for about a year now so I expected improvements.
Second, what impedance will your receiver drive properly on the sub channel? What impedance are the Kickers? To high and you don't get the rated power. To low and more current flows than the receiver is designed to handle. Poof and you release the magic smoke from the receiver.
Finally, have you ever designed a subwoofer enclosure? Are you familiar with the Theile/Small parameters? It's not the car sub vs. home sub because that is just marketing. You have to look at the parameters and design the enclosure to meet your goals. Sometimes you can't. I use subs that were first marketed to the car audio people - http://web.archive.org/web/20070216221746/http://www.tcsounds.com/tc3000.htm . Two 15's, each in it's own sealed box connected to an amp capable of 800w at 20hz.