Try changing your tubes to a different brand/NOS first. I don't think your going to see that big of a difference moving to the 12000 from the 2500, better DAC of course. and the option for SS or Tube stages if that's something you like. I did a comparison from the 2700 and 12000 and the difference did not justify the price difference to me, tube stage comparison only.
Tubes made a good difference with my 2700 when I was tube rolling. definitely able to tailor the sound more with different tubes.