Amps or Speakers which one to upgrade next

better masterings, yes

or bigger, better Vandies

What is the rest of your setup??

+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.