Wheatfield, unite!
I built two m³ (one for opa637, the other AD8610) and a Millett Hybrid. For fast, it's the m³ hands down, and good power (STEPS) makes all the difference. But, there is just something about that Millett Hybrid that is more, er, harmonic... hence, I moved to it's pumped up cousins, the Wheatfields. You _could_ build one (HA-1 or HA-2), as the schematics are posted on Pete's site.
But, you can't go wrong with the m³.