Amps or Speakers which one to upgrade next

Neither. Put all of it into power and power cables, as a first step. It will transform your system, and once you make the investment, it is there for any component changes in the future.

Your room looks like it's multi-use...and since it is a partial pic, I'm not sure what you've done with the room. That would be the other area to invest in.

Nothing will give you a bigger difference than changing the speakers.  You get the most bang for your buck that way,  Replacing an amp will make a very small difference compared to changing speakers.  I would explore that aspect. I had Vandersteen for over 20 years and that was before they had all these different models.  If you like their house sound, go a notch or 2 up the food chain.

++ @jond 

Well, upgrading both might be better, theoretically, but the question is would $7k plus the value of what he has now be enough for a jump ?

Great suggestions from Jond!   He did your homework.  I could have used that in school! 

IMO be careful if you are happy now, once you change one thing it will most likely soon snowball into another, then another and so on....

To quote Paul McCartney "happiness is a warm gun"