I once had a KPA head. I need to fly low budget so I checked in my Strat (neck unscrewed inside the suitcase) and took the KPA head into the cabin. Then the rack version came out and I thought: "wow, that´s much more practical!" After two years I sold the KPA for some other reasons and since then I travel again schlepping a small tube-amp with me.
Now I am decided to buy a KPA again but I am not so shure whether the rack really is the best choice for me. It certainly is ideal for musicians who tour with an equipment truck and a roadie-crew but I am more touring small club-gigs where I myself have to carry all that I need in trains and busses and airplanes. I read the rack KPA needs a 4 unit rack case because of the heat dissipation. (I want the powered version). A 4 unit case might be a problem with finnicky check-in controls, the height exceeds the stupid 55 x 40 x 20 cm rule.
The head weighs half a kilo more than the rack but if you carry it close to your body it can go inside a simple bag and only needs a little foam to protect the dials. The rack is much more bulky and heavy if you include the case in the equation.
I am thankful for any hints, advice and reports from your point of view.