At around $30, the Lepai LP-168HA (buy from Amazon) is a cheap 2.1 amplifier that can function perfectly as a dedicated amp for a subwoofer.
A friend of mine recently came across a pretty good set of speakers that seems to have come from a home theater in a box, but not the receiver. The speakers will work fine with any old receiver with the exception of the subwoofer. Since it's passive, it can't be plugged into LFE output of modern receivers.
My friend is a student, so the solution needed to be cheap. I did some research for him and came across the Lepai LP-168HA. He's currently got his left, right, and subwoofer plugged into it.
When he gets a receiver, he'll just use it as a subwoofer amp. To do so he'd just need to run the LFE to oneof the RCA input jacks on the back of the Lepai LP-168HA and make sure the speaker cable from the passive subwoofer is plugged into the corresponding channel.
- Super cheap, it's $30
- Small and powerful
- Separate amps for subwoofer and left/right speakers
- Separate volume controls for subwoofer and left/right
- RCA input and 3.5mm input
- As many of the Amazon reviews have said, the crossover doesn't work at all, function as if there is not one, but that won't matter when the crossover is being handled by a receiver
- Insanely bright LEDs
- Separate volume controls for subwoofer and left/right can sometimes make it a pain to quickly adjust volume
Buy from Amazon