There is a diagram on page 107 of the Main Manual showing that setup.
You feed the inputs of the stereo power amp from MONITOR OUT and DIRECT OUT.
You connect the KEMPER Kabinets to the speaker outputs of the power amp. I guess, the power amp can deal with 4 ohms each side.
You enter Output Section and activate "Monitor Stereo" as well as "Kemper Kone".
To use the Speaker Imprints, activate "Monitor Cab. Off", too.
More details related to Kemper Kone settings are in the manual.
Depending on the wattage of the power amp, you might want to be cautious with "Power Amp Boost".
Thank you very much Burkhard!
Why is it the Monitor and Direkt OUT? why not the Main/Master Outs?
So If i set "Monitor Cab. Off" the Profiler will no longer "simulate" Cabinet-tone coloring?
And which output is for left and which for right stereo-channel?
I will definitely not need the "Power Amp Boost" because I will play for myself in my basement. 
It's worth reading the chapter related to the KEMPER Kone. It's all in there.
KEMPER Kone Mode only works at the MONITOR OUT (and DIRECT OUT if it's paired with the MONITOR OUT via "Monitor Stereo").
Without Monitor Cab Off, the KEMPER Kone runs in full-range mode, so you hear the cabinet PROFILE. With Monitor Cab. Off it runs in Speaker Imprint mode, so you hear one of the Speaker Imprints instead.
MONITOR OUT is left and DIRECT OUT is right.
You will also need to use speaker cables (not standard 1/4 instrument cables) to connect the power amp to the Kabinets
External Power Amps Driving Unpowered KEMPER Kabinets
If you want to use unpowered KEMPER Kabinets but have no PowerHead nor PowerRack, you need an external power amplifier. Any solidstate amp wil l work. Using a tube power potentially sweeten the sound too much.amp will change the frequency response and Mono/stereo setup with PROFILER Stage and external power amplifier.
And as stated above, instrument cables from the Profiler outs to the power amp inputs.
Speaker cables from the power amp outs to the Kabinet inputs.
Thanks so much for clarification!
MONITOR OUT is left and DIRECT OUT is right.
But the picture in the manual as HowardBrown showed, shows the left speaker connected on DIRECT OUT. So the picture is wrong went it comes to the left/right representation?
Big thanks also to Kellerblues and HowardBrown !
And as stated above, instrument cables from the Profiler outs to the power amp inputs.
Speaker cables from the power amp outs to the Kabinet inputs.
Whats the diffrence?
Now I have to find out the correct german titles of those cables. Because when googling for "speaker cable" alot of different cables pop up...
But the picture in the manual ... shows the left speaker connected on DIRECT OUT. So the picture is wrong ...
Depends on how you look at it 
If you setup your Kabinets as your backline (behind you, facing the audience) it's correct (for you, as the guitarist).
If you use the Kabinets as monitors in front of you, facing away from the crowd, it's "wrong".
So, what's the more common scenario?
Whats the diffrence?
Now I have to find out the correct german titles of those cables. Because when googling for "speaker cable" alot of different cables pop up...
Look at this link:
Ah okay, those are speaker cables, they have the same jack as instrument cables okay.
So from KPA --> AMP are instrument cables
And AMP --> Cabinet are speaker cables
What about their length? which one should be short? or does it not matter? The total KPA --> Cabinet cable length is going to be something like 5 meters. Is 0.5 meter instrment und ~4 meter speaker cable recommandet? or should be the AMP as close as possible to the Cabinets?
Or should it bie 1/2, 1/2?
Thanks alot! 
Up to 5 meters total length it is up to you how you split it.
TS ... mono
TRS ... stereo
Kemper Cabinet Out ... use it for daisy chain 2 cabinets, see Main Manual 8.5 page 104
