chefp2010,
I'm no expert on this stuff, certainly not on Audyssey, and frankly don't know why some power decided to designate me as "somebody who should be listened to". As with anything on the internet, you are right to question anything you read.
I can tell you I only use Audyssey for 2 things:
1) Setting speaker distance
2) Setting a starting point for individual speaker volumes
By far, I think speaker distance is the key parameter set by Audyssey. Your brain perceives where a sound is coming from because of the split second difference in when a sound wave hits each of your 2 ears. (I assume you do have 2 ears.) Your brain detects the difference and uses it to calculate if a sound is coming from left, front, right, etc. Pretty amazing.
When a sound is generated to seem like it's coming from straight in front of you, that sound is sent to the left & right speakers at exactly the same time. So when the sounds hit your ears at exactly the same time, your brain calculates it is coming from directly in front of you, and it sounds like it is coming right out of your TV. Now suppose your front left and front right speakers are not exactly equidistant from your listening spot. The sound will not hit both your ears at exactly the same time, and your brain decides it is coming from left or right of center.
This is why speaker distance from your primary listening position is important. It applies to fronts, surrounds and rears... any speaker pair. Audyssey detects exactly how long the sound from each speaker takes to reach the microphone, (your ears in the primary listening area), and adjusts the sounds to each channel so it "sounds" right when you hear it. So the speaker distance setting within Audyssey is the single setting I never change.
(The subwoofer is different because of the looooong wavelength of low frequencies. The wavelength is long enough that the distance between your two ears is too short to detect any difference in when the wave hits them. It is why you can't tell where a very low sound is coming from. If you use 2 subwoofers, Audyssey helps w/ phase matching, but is not necessary with only 1 sub.)
Audyssey volume for each speaker is a good starting point, but your preferences may vary for any number of reasons. If you decide a speaker is too loud or too soft, don't feel bad about changing its volume to something you like.
All the other stuff in Audyssey is stuff I change. Speakers to "small", and crossovers to recommendation by speaker maker. However, I don't have any experience with Def Tecs, or speakers with built-in subs. I would guess you treat the subs just like you would separate subs, but I'm sure some people here can give you more specific help.
