Amps or Speakers which one to upgrade next

+1 Randy
A pair of used Quatro's would definitely be in the price range and you'd get a sub, too. Otherwise, I would get a pair of 2wq subs for your 2 sigs.
to fill out the bottom end.
Bob

The rest of my system a Clearaudio Performance DC w/ Clarify arm
Talisman cart. Musical surroundings Nova II and Oppo 103 w/        Ayre Codex
You can check out some pictures under systems 

If you like the sound you have now but want to make it even better, most likely it is a much better amp and source that you want. But I would probably start with tube rolling and trying other cables. Rogue is a value brand, it is not high end.

I daresay if spent wisely you could upgrade your amp AND your speakers for $7K. Perhaps something like this:

https://www.audiogon.com/listings/tube-line-magnetic-518ia-extra-tubes-mighty-845-set-magic-2017-11-...

And since you like Vandersteen you could do this:

https://www.audiogon.com/listings/full-range-2017-11-07-speakers

Though I personally also like the looks of these:

https://www.audiogon.com/listings/full-range-odeon-tosca-gorgeous-german-horn-speaker-2017-11-26-spe...

And these which as an Audio Note owner I can highly recommend:

https://www.audiogon.com/listings/monitors-loudspeakers-2017-11-17-speakers

That was a fun exercise that took just a few minutes poking around the site, obviously just a few things I like our tastes may differ. My best advice would be take your time, do research, listen if you can, and try to buy once and buy right.  Good luck!

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.