So there's this huge argument that says "2-channel audio is the way to go". If you look at spending $2,000 and have a choice between a 2-channel integrated amp and an AV Receiver, it is very likely that the 2-channel integrated amp is going to sound superior. That is the entire premise for millercarbon's argument. If you are going to use this system for 70% or more "music only" listening, this could be the way you want to go.
However, there are problems with the "2-channel only" approach if you are heavy into watching movies. Whatever source components you have, the entire 5/7 channel source has to be down-mixed into only 2 channels. This presents problems.
This is a VERY EASY experiment to make.
1. Pick an action movie that you are very familiar with and watch a 10 minute progression where there is a lot of sound going on.
2. Go into your Pioneer receiver configuration menu and disable the surround speakers.
3. Re-watch the same 10 minute progression.
4. Go into Pioneer configuration and now disable the center channel.
5. Watch the same progression.
This will show the type of sound you will get when playing movies through a 2-channel only system. If you are okay with this type of sound, then by all means go with a 2-channel only audio rig. The compromises are basically the following:
no center channel - Basically you lose a lot of clarity and solidness in the dialogue and anything coming. Millercarbon's argument that you don't need a center channel is all based on absolutely perfect room acoustics and sitting your butt down EXACTLY at the center point between the left/right speakers. However, just move to the side 5" and you're whole center channel image is completely lost. You can try this experiment in your own situation. This is compounding by the fact that the center channel dialogue is cut by 50% and then sent to each left/right speaker, so if you are off center, that "center channel dialogue" will be quieter and actually harder to hear.
no surround channel - I have had problems on 3-channel systems that do not have actual surround. If you down-mix the surround channels to your left/right speakers, what happens is that the left/right become increased in volume and will have an "echo" type of effect. The second problem that occurs is that your center channel dialogue becomes extremely difficult to hear/understand because the overall volume of the left/right speaker totally overbears any sound coming out of the center. You can fix this if you use an HT processor just by enabling the surround speakers (even if nothing is connected). You will obviously not hear the surround effects, but it gets rid of this problem. However, the surround speakers actually make the entire sound stage much bigger. If you disconnect the surround speakers and listen, the whole soundstage becomes smaller since your soundstage is only the front of the room (almost like converting a stereo music song to be played as "mono").