Stereo power amplifiers. Bryston, Hafler, Crest, Crown, Mackie, Peavey etc. all make a bunch of models at different power (wattage) levels. They take a line level signal, and raise it to speaker level.
Your home theatre reciever probably (in fact, certainly - if you connect speakers to it) has a power amplifier stage. It also has a lot of extra circuitry that you don't need, and isn't really the best tool for the job.
Scott