Most full range speakers on the market are powered but tend to come with unto 1000w so don't worry about needing a 600w power amp for full range. The real advantage of the power head is that you can plug straight into a regular guitar cab if needed. As others have pointed out, I always try and avoid this and very rarely play anywhere that doesn't put the guitar through the FOH PA. It gives much more control and generally better overall mix than running off back line (especially if running a 412 on stage - those beasts are the work of the devil and should be outlawed ).
The Kemper powered cab I saw is only 200w.
I don't mind using a 412.
I still think nothing sounds as fat and smooth.
And I used to gig modeling amps and full range speakers for years.
I noticed a live tonal improvement that was noticable when I went back to tubes.
This is my chance to dive back out of the tube world.
But I did talk to the guitarist of VH Nation. Great guy and knew his stuff. Said he has the full range setup and has run direct but disnt like it as much as using his 412.