Apogee Acoustics Caliper,which amp?

None of them are the last word in current. The McCormack will probably sound best in the bass and the midrange. I doubt whether either of the other two amps really have sufficient current to make the Calipers sing. Apogees need both power and current. Borrow a Krell of 200 watts or more (not KAV series) or an Aragon 4004, if you want to better understand what current and power can do with Apogees. Keep in mind that you may have to experiment with cabling to obtain a sufficiently musical sound.

Forget the Yamy, Try a Krell, Mark Levinson, Classe, Bryson Etc 100watts or better, Look for doubling down to 2 ohms or even 1ohm. If on a budget a old KSA krell 100 will deliver 800 watts into 1 ohm. Classe DR 250 is another good amp. Also sunfire if you want new stuff at reasonable price,

Apogees seem to work best with Classe Audio amplification, Dave and Jason worked well together way back when...

try 4004mk2 or krell ksa100