Affordable musically fast subwoofer

I am looking into acquiring an affordable and musically accurate subs, which will pick on the lower end notes of my Horn loaded single driver fullrange speakers. Besides those terrible 100+lbs subwoofers that retail 2-3k, is there something out there that is not necessarily hernia producing but that will actually be quick and musical enough for my horns?
The RELs are too expensive....decent used ones about1k+
The ACI Titan, seems to be decent, but still too heavy and moderatedly expensive at 1K+
The VBT Magellans, sophisticated, but the full set up, I wonder how good.
what about those mini SUNFIRE subs?
Any other ones that are easy to acquire in the used market?
Vandersteen 2W.You run the sub off the amplifiers output thus retaining the main amps signature in the sub.Great price used also.If you really want to do it right I suggest building your own.You will learn exacally what it is you desire in a sub by building your self.The flexibility in chosing a driver, encosure and what amp to drive it along with the proper equalizing(parametric).There is a trial and error period but that is where you learn what about bass you like.How about an Adire Tumult sealed.An Adcom GFA 555mkII amp (bridged mono).A Behringer digital parametric and you have world class for under 1000.00.Good luck.
VMPS is well known for some of the best bass available. Prices are very reasonable. Check out the site:
You can find out more at the VMPS circle at
The designer, Brian Cheney, has been known for over twenty years as offering some of the best bass available and things haven't changed. Prices are great bargains for what you get. These are passives so will require an amp, but that's easily affordable considering the price of the subs.
I have a Parts Express $100 special in my basement home theatre system. After breakin I have to say that I like it in that capacity, a lot. Now, I don't listen to music in that system - only movies. YMMV

I have a REL Strata III in my main rig and it certainly blows away the cheap sub. But the REL wouldn't work in the home theatre system at all. Each for it's purpose according to its strengths.

Used Velodyne servo sub F series (e.g. fsx 12). Not real small, but definitely under 100 lbs. Run my Spicas full range, keep the crossover low and its closer to audio nirvana than it deserves to be.
Subs don't have to be "fast" (a bass note is quite slow in attack) they have to be "clean".

A lot depends on where you are crossing over. If you are crossing over at, say, 70hz or below the HSU VT3 is invisible and has great deep basss at around 800 bucks. If you are crossing over at a higher frequency I might rather go to a sealed box type. The Martin Logan ones are very nice (if pricy).

The trick is, the decay characteristics of the sub have to match the mains or it just doesn't gell. For instance, my speakers only sound integrated with ported subs; sensor-controled and sealed boxes just would not match no matter what I did. On the other hand my friends sealed box speaker sounded best with a sealed type sub.