I have the Concierto working under AHI 6 in OS3.9, and the Toccata needs a specific >= toccata.library v12 to work which I haven't gotten around to.
As to which one supports AHI better, wouldn't most of them (if they have an AHI driver) support pretty much the same features except different sample rates? Not an expert on AHI, but maybe some are able to support more AHI channels too? (especially hazy about the channels part as it may only depend on CPU....)
Yes the Toccata is indeed a nice card, though not the best of the best. There was a thread on here somewhere not too long ago about the best soundcard for the amiga.
I think there may be one or 2 amiga sound cards with "better" output than a soundblaster live.
Best bet is to browse the listings on the 2 amiga hardware sites:
You will come up with some good SNR, sample rate and data bits and AHI compatibility for some sound cards.
The Repulse soundcard and Kato Development Melody 1200 Pro (+ optional Digital I/O module) both seem good, and are both listed as having AHI drivers.
I believe the SNR of 95dB quoted on the hardware site for the toccata may be incorrect, as the manual lists no SNR, but lists the dynamic range as 95dB. Anyhow, the Melody 1200 is claimed to be SNR 108dB.