Spectron Musician III MK2 vs Carver Sunfire Signature vs Adcom GFA-555ii Infinity Kappas?

Hi All,

I have a pair of Infinity Kappa 8's and 9's I am trying to drive adequately.  Music I am listening to is primarily 60's-90's rock. I am interested in dark, liquid, highly holographic sound. 
I have not tried a Spectron yet but so far the Adcom GFA-555ii is favored over the Carver. The Adcom seems to really take hold of the Kappa 8's, mid and upper bass are tight and palpable. Treble is a bit too sibilant but overall minimal distortion is apparent even at high volumes with the Adcom.

The Carver using the Voltage Source works well to reduce sibilance of vocals (think Peter Gabriel and Peter Gabriel Genesis) but I swear I hear lots of distortion and compression with this amp. Stereo image flattens out a bit with the Caver amp as well.
Is it worth trying out a Spectron and/or two Adcom GFA-555ii in mono?
Any other thoughts on amps that are going to be able to handle Infinity Kappas (which get down into 1 ohm range), will be gentle with sibilants and have an highly holographic soundstage?
Thanks,
Brett