I haven't owned the Sonic Frontiers Power 2, but have owned the Sonic Frontiers SFS-80 (80 wpc) and now own the V-4's.
My experience with the SFS-80 & the V-4's have both been great. Both are built like tanks, good reliability, easy biasing, and both have decent drive.
I have only heard the Power series in showrooms, which was when I had my SFS-80 and always thought they sounded a little less "tube like" and more analytical. Perhaps some liked that, to me though it was a move in the direction away from which they established themselves. Not my cup of tea.
I think I have stated before, I prefer my tube amp "sonic signature" to be just a slight bit on the warm side of neutral.
The V-4's I currently own are configured with KT-90's and Mike Sanders told me he tested them at 170 wpc before he shipped them. I am running 4 Ohm 91 db speakers at this time, but by no means are they short of power! I can barely use 20% of the preamp volume control... They seem to have an amazing reserve of power & control.
If you decide to go the Sonic Frontiers line, I would suggest looking for the SFM-160 monoblocks over the Power 2's from what I heard *and remember* with my ears in the past.