I use the 'power' outlets to feed two Arcam power amps, and have never noticed any diminution of perceived power or of dynamic range, or any lessening of the sudden transients that good hifi is capable of delivering. I'd agree with 'try before you buy' if you are able, but this problem isn't one I've heard of or experienced in connection with IsoTek/Isol8, and I do know other users.
The plusses are an improved sound across the board, though the depth of soundstage is the thing that (no pun intended) leaps out at you.