I'm a big believer in amp/speaker synergies. So it's fairly useless to talk about amps in a vacuum without considering what they're driving.
For instance, the Atma-Sphere S-30 is said to be a heavenly match with Audiokinesis speakers. So maybe a speaker switch is a better bet than an amp switch.
Similarly, the Quad 57's sound fantastic with McIntosh MC225's (my dad's setup). When I had some later Quads (63's) they sounded extra nice with an OTL Transcendent Sounds amp. And quite good with a lowly Dynaco ST-70 too.
On the other hand, my Maggies sound too laid-back with McIntosh, but really come alive with an Innersound ESL amp.
I extensively auditioned a pair of Green Mountain Audio Calypso's (GREAT speaker), and those were nicely driven by a VAC Phi integrated.
My point is that the amp technologies need to match the characteristics of the speakers to obtain maximum sonic benefit. So it's helpful to know not only where you are going with your amp choices, but where you are coming from, and the speakers that are your partners in the process!