I'm gonna go slightly against the trend here..
I would say, don't jump into FRFR speakers/cabs just yet.. or power amps either.. In fact you may not necessarily need to buy a power amp at all just yet either.. You already have a power amp = your Valve King.
You can run the Axe FX thru the RETURN of your V.K's effects loop.. By doing this, you're using your V.K as the power amp; it's only purpose is to give you 'valve' or 'tube' push. Why do this? Well, with so many awesome amps within the Axe, you can get a good, strong, true valve tone via your VK but use the Axe to do the rest of what, for example, a Mesa Recto can do, or a JVM, or Friedman Dirty Shirley, or a Cameron CCV, or a 5153 etc etc.. The Axe will give you the amp simulation, your VK will give you the power.
THEN, if this proves to be good and you're happy with it, you can then go down the path of buying a power amp (be it valve or tube), OR, eventually start experimenting with FRFR speakers/cabs..
STRONGEST suggestion.. avoid getting into FRFR straight away.. experiment with 'normal amps/cabs' before going FRFR. I think FRFR can take some time to get used to.. For some, they love it straight away and for others it takes time to get used to. Your ears will be your best judgement.