There can be too much of the tube sound in a system, but the only way you're going to know is to try an in home test and hear it for yourself.
As for your other quandry, you can upgrade the DAC with an Audio Mirrod D1 ($500 on Audiogon) and use the 640, MH, or Rotel with it. You may even consider the AH!, but it might be overkill. I considered the Jolida JD-100 with the Audio Mirror so I could switch between tube and solid state. Just a thought...