power amp/pre amp input and output impedence question

"Same for poweramp to speaker."

????

What are the effects of a mismatch 

what effect can be expected from a miss match.

What does an output impedence of 1.2k ohm say to the expert......

If the ratio is less than 10:1 you might have less headroom before the preamp makes distortion. There would also be more overall distortion so less detail and probably harsher sound.
An output impedance of 1.2K ohms isn't bad. You can drive amps with 20K or higher input impedance no worries. The thing to look at is the output impedance at 20Hz. Many preamps have acceptable output impedance at 1KHz but at only 20Hz their impedance can be quite a bit higher. If at this frequency its less than the 10:1 rule of thumb you might experience less impact in the bass.

"Same for poweramp to speaker."
????

Yes "damping factor", stretching this one a little, but the lowest impedance of the speakers curve can also have the 1:10 rule applied to it that the amp is 10 lower than it or even better.
So if the speaker is 2ohms in the bass the amps output impedance "should" be 0.2ohm or better lower at that frequency also.

Then in there’s the capacitor coupled components, these need to be looked at first to see if the cap is big enough to maintain the 1:10 rule, if not there could roll offs at the frequency extreme

I notice as i research amps and preamps, sometimes these specs are hidden away or non existent in the owners manual  :0/
 
Why would they not include these important numbers ? Is this kinda like when a manufacturer says an amp can put our 1000watts/ch @1Khz and not a full bandwidth watts/ch, not just a convenient 1Khz signal which is fairly easy for the amp