I only have a very fuzzy understanding of a pre-amp vs an integrated AV Amp vs an integrated Stereo Amp....
Can I connect a stereo sources to a stereo pre-amp...
Chin-Tuan,
There are 3 things you need to hear music/tv/movies from your speakers.
1. Source
This could be an MP3 player, a radio tuner, a CD/DVD/Bluray player, a TV, etc. This is the actual source of your sound.
2. Processor
This takes the signal from your source(s) above, and turns them into an analog signal. This "analog" signal is the format your speakers require. So the output of your processor is in the right format for your speakers, but it is not strong enough.
3. Amplifier
This takes the signal from your processor and amplifies it to a level strong enough for your speakers. Wires run directly from your amp outputs to your speakers.
You need all 3 elements above to hear anything from your speakers. An "AVR" takes care of #2 and #3. And it can have a radio tuner so maybe it does a little of #1. Usually for #1, you'll need some other stuff, like a TV, a CD/DVD/BD player, and an internet connection for stuff like Pandora.
Or, instead of an AVR that does all of #2 and #3, you can get separate components. A Pre-amp, or Pre-amp Processor will do #2. It will take all your digital inputs, (radio/tv/cd/etc), and turn their signal into the analog format. Then a separate Amp will take the ouput from your Pre-amp and do #3.
Since an AVR does both Pre-amp and Amp function, you don't need an AVR and a Pre-amp, or an AVR and an Amp.
Like I told you earlier, some AVRs have outputs, "Preouts", that are taken before the AVR's amp section. Essentially they let you bypass the AVR's amp section and use your AVR like a Pre-amp. So you CAN use an AVR and a separate amp if you want.
One more thing. You mention "stereo" several times. "Stereo" simply means 2 channels. MOST music is produced in 2 channels. MOST TV and movies are produced in 5 channels.
So a "Stereo" pre-amp simply means it can only handle 2 channels. A "Stereo" amp simply means it can only handle 2 channels. A "Stereo" AVR, (if there is such a thing), simply means it can only handle 2 channels.
But it is entirely possible and reasonable to only use 2 channels for music listening through your 5/7/9/11 channel AVR, Preamp or Amp. In fact, most of us do. For music listening, we simply select "Stereo" on our AVR. This makes the AVR process all input into 2 channels, and provides output to 2 channels. Changing from Stereo to multi-channel is usually a 1 button click on the remote.