How to match preamp and power amp?

How to match them by looking at the preamp output impedance and the input impedance of the amp? Any magic numbers? I don't understand their relationship. Please help.
How to match preamp and power amp?
To determin "if" you need passive preamp (no gain) or an active preamp (with gain). There was a test that was a very good indicator, and that was the "Revels’ Bolero Test". This cd starts off extremely quite for quite a while and builds slowly.

You do a direct connection between source and poweramp (no preamp) making sure if it has it the source’s volume is up full.
Switch everything on and press play to start "Revel’s Bolero" just for safety have your finger ready on the source’s stop button if it gets too loud as it get’s into it.

If it get too loud or is way over your normal listening level, then a 10kohm passive preamp will do you fine, like the $49 Schiit Sys. If your poweramp has 33kohm or higher input impedance.

If the sound is not loud enough even over 10mins into "Revels Bolero" then you need a preamp with gain, a Schiit Saga or Freya are great buys also, these can also be passive as well as active

Cheers George
@RPNZ: Cary Audio's published specifications for the the SLP98 show the output impedance at 440 Ohms, not 800.  Yes, I know this is an old thread.
Ok - So I have a Copland CTA301
    Output load 2. 8kohm
     Output voltage (at the time of 47kohm load) Rating: 2V Maximum: 50V
 And Caspian M2
   Input Impedance 38 kohms
    Input Sensitivity 240 mV rms

Would that work?

I need help so this topic is right for me I had m8s500 power amp I bought

The m8 preamp musical fidelity the sound is horrible didn't know it was going to sound that bad I thought that it was the right match what preamp should I buy for this m8s500 power amp