I have an Innersound ESL-300, a Bel Canto evo-4 II, and a Crown K2 amplifier. The Bel Canto is my favorite as it is the most transparent, has better clarity, seems livelier than the Innersound, and does a better job with spacial cues.
The Innersound has some strengths; it is a hint warm'ish (richer or fuller) through the lower registers (which is often a good thing), a bit smsoother overall, and seems to have unlimited power - unfazed by the load. And it produces a rock solid image. However, I miss the immediacy, the "reach out and touch me" palpable sound that the BC provides. The Innersound falls short in this respect. The BC can sound lean'ish with some music though, when the Innersound sounds just about right and better filled out. So it's not a clear cut victory for the BC in every case.
Verdict: The Innersound is an above average ss amplifier that is well worth $1K. Not perfect, but no glaring faults. Without something to compare it to directly, you will likely not notice any weak areas. It's an easy amp to live with.