Stereo amplifier for a pair of passive subwoofers.

I want to drive the bass drivers on my speakers to reproduce the LFE from my Denon AVR-2805. I'm trying to find an used amplifier that can do the trick but I'm confused with so many model/brands and could not decide. Is there anything from the actual list under $400 that I can pick? Can a Hafler, B&K, Muse, Acurus, Parasound etc be a good pick? I will apreciate any help....
A used Bryston 3B ought to do the trick.
Ditto the Bryston 3B
a parasound thx amplifier is a bargain on the used market and many of the models have seperate volume controls for each channel which can be useful with passive subs
I use an Onkyo M-504 (around $400 used) along with a Paradigm X-30 crossover (around $100 used) with my passive subs. Depending on your setup and needs you may not need or want the Paradigm x-over.

Second the Parasound BUT you would not want to send the LFE channel to your main speakers. Instead you would want to set your main speakers to LARGE in the set-up menu and your subwoofer to NONE. If you do in fact have a subwoofer you could simply amplify your main speakers with something like a Parasound HCA-1000 and use the loop outputs to feed the sub a stereo signal. Assuming your sub is placed right and of decent quality you will get the desired affect.

Good luck!
I use to use a Bryston 4b with a PAradigm X-30 for my NHT SW3P and found it to be superior to the companion NHT SA-3 amp. I didn't think either crossover was that good, but the Bryston as a sub amp exhibited great control and depth while helping the SW3P produce good tone.
Both Bryston and Parasound have been well know to do well in the bass department. You'll not go wrong with either. It's all a matter of finding the good deal for you probabaly.
Especially if you're buying used, remember, Brystons come new with a 20 year TRANSFERRABLE warranty! A big plus for used buyers; and they are extremely acommodating about service/upgrades with no charge for under-warranty products.
the bryston would go to the top of the list based on the warranty; agree
Well, everyone agreed on the Bryston units and I know these are tremendous amplifiers. Their 20 years warranty is incredible, although they last longer than that !!! The problem is, every unit ( except from EBay) seems to be around $700 or more. In which case, I would buy a SVS or Hsu subwoofer to pair my existing speakers ( Madisound Geminies- Dynaudio clones).

My mistake was not to mention my initial thinking. My stereo speakers consist of a pair enclosures where the highs/mids are on the top box and the bass driver is in the lower box. Since I could use them as passive woofers, I thought I could buy an under $400 amplifier and use it as a sub-amplifier. This way I could use my top boxes ( which extend to around 50Hz) as small and use the bass boxes to reproduce the lower frequencies.

My room has around 5,500sqf and a single subwoofer seems to be short for the space. With the towers using both drivers, I could fill the room better. An used amplifier looks like my economic alternative or buying a big sub from SVS, Hsu or Velodyne...which cost way more and shipping will set me another $150+ for one and double for two ( the avarage cost of a used amplifier).

I still love the idea of a Bryston but, unless I find one good deal, is out of my range...$$$

Gracias all :)
You have a great number of options in this price range if you buy used. Everything mentioned above has potential. You might also want to consider a pair of Marantz monoblocks for around $300 used. If you want to try Hafler, let me know. I have one that I was planning on listing shortly. Have fun with your search.

Ok, this is what I found available under $400:

Acurus A200 ...........$400.00
Hafler DH-200 .......... 225.00
Rotel RB-980BX (2)........ 295.00 and 325.00
Hafler 9300 Trans Nova .. 375.00
Acurus A150 ................325.00
Parasound HCa-1200 .... 375.00
Hafler DH-220 ............. 200.00
Acurus A250 ................$400
B&K ST1400 .................250.00
Muse Model 100 ...........400.00
Hafler XL-280 Excelinear ...350.00

What should I consider?
How about a used Carver ZR series amplifier. These babies really have great control over the woofers. Or maybe even a Peavey GPS series . Both amplifiers are absolute work horses.

Good Luck!
The trouble with inexpensive amplifiers for subwoofers is that they tend to be deficient in exactly places where you need them to be strong: power rating and/or power supply. Big transformers and big capacitors are expensive so that's usually where the cost cutting takes place for inexpensive amps--high power rating don't help much with puny power supply.

You may want to consider finding an inexpensive class-D switching amps using 250-watt or 500-watt ICE modules or similar modules. They don't require large power supply and the inexpensive one don't sound good in the mid and high frequencies but you don't care about that. The bass will be the best that you can get out of solid-state amps.

Unfortunately, I am not familiar with the many small manufacturers that make these amps inexpensively. But I think it is well worth your time to look for them.
A lot depends on the subs used as far as how much power your going to need. My power meters on the front of my Onkyo M-504 very rarly hit peaks of over 100 watts driving two vmps subs.

Most of the time the Onkyo is coasting along at well under 100 watts...more power would be nothing but a waste of good money.

I should mention also that this is in a large room.

Sogood51, transient power peaks is also a very important parameter.

Yes, most of the time amplifiers just coast along around 5-10 watts. But even within that period, there are transient signals (in milliseconds, too fast to register on power meters) which can consume huge amount of power in short bursts. That's what the extra dBs of headroom is for.

Typically, most good power subwoofers use amplifiers in the 250-500 watts range. Some, like the new Velodynes DD use around 1,300 watts (Class D amps). If space, weight, heat dissipation (for class A/AB amps) and cost weren't a problem, subwoofer manufacturers would probably use even higher power amps.

Well shure, and my Onkyo has over 300 watts a side for my 90-91db VMPS's. As I mentioned, the subs design along with the size of the room they will be used in play an important factor in the amount of power that will be required. Also, I use two subs for stereo and three for hometheater.

A single sealed sub in a large room may indeed need huge amounts of power to reach high spl's.