A lot of integrated amps have jumpers between the pre-amp output and the power amp inputs. So, you can get at just the power section by removing the jumper and plugging straight into the power amp.
Notice the back of this NAD amp, has both a jumper between one pre-amp out and the power amp ins, and a separate pre-amp out to drive things like subwoofers. The Power Amp input are labeled MAIN.
http://nadelectronics.com/img/resamp...-C355_rear.jpg
Now, if you don't need to use the stereo power amp as a stand alone stereo, the indeed a power amp is OK. But, if you plan to run the stereo without the AV amp when playing music, then you are going to need an integrated amp, and you will need to use the standard Line In (AUX, TAPE, CD, DVD, etc...) inputs.
It is really just a matter of deciding if you need just power, or if you need an integrated amp. Then, look at amps that you like, and see if they have this break between the pre- and power section. Of course, with purely power amps, this isn't a concern.
Steve/bluewizard