Krell was the go to when the Apogee's were new. FWIW, I much prefer Krell to Levinson and especially McIntosh. Depending on the particular Apogee's keep an eye on the specific minimum impedance. Not all of these amp manufacturer's amplifier models are necessarily suited for all Apogee's. You might want to consider some Classe' amps as well, though personally I still prefer the Krells.
