I have had my AR9's since I bought new in 1982. I used to drive them with a Yamaha M-2, then a M-80. I have gone to a Canary Audio CA-301 mkii 22w 300b tube amplifier. Much better sound and never any lack of power... deep controlled bass, beautify mid and high.
I also use Synergistic Research Resolution Ref cables... wonderful upgrade to sound.