Is it worth it?

"But a $5k speaker and a $15k amplifier, I would probably go the other way around, and seek out a $15k speaker and a $5k amplifier.  I think you will get a far bigger bump in performance that way."

+1! I can tell you from recent, personal experience ... your speakers are THE most critical electronic component of your system. 

You’ve got damn good speakers that punch way above their class. Unless there’s something you don’t like about them you’ll have to spend a lot more to exceed their overall build and SQ.

Just me, but I don’t believe these VTL’s are better than the Pass amps. If you could do an A/B comparison that would tell you clearly which would sound better in your system. 

But the Pass .8 amps are top of the food chain 

 powerful VTL amps run very hot even in triode mode. normally in triode mode tubes run warm and safe to touch or definitely you can feel difference of air temperature barely close. In Ultra-Linear mode it's fireplace.

I don't think you need to spend that much money to get great sound from the F208s.  I have had my F208s for about five months.  I power them with Primaluna Dialogue HP integrated with KT150 tubes.  It sounds fantastic!  And, the amp was around $5k with the tubes.  

If you wanted to step it up, you could go with PL Dialogue HP mono block amps, and it would run around $7500 new and sound fantastic!  

I think spending all that money on the Pass amps is overkill for the F208s.  You can get seriously great sound for far less money, and have left over dollars to spend on music.