When I had AR9 speakers set up a decade or so ago, I used the amplifier sections of two Onkyo TX8500 recievers (dual independent power supplies) in vertical bi-amp mode. They worked great. Unfortunately, I had to sell that pair of speakers. I am finally getting around to rebuilding my 2nd set of AR9s; the upper section is ready, a professionally is refoaming the woofers, hopefully I'll get them back on Saturday.
I am concerned that the TX8500's may need some refurbishing, I got estimates in the $500-$600 each range from a couple of places here in the Bay Area. I am not ready to pull the trigger on that, and am considering purchasing a digital oscilloscope instead, and doing it myself. Of course, I don't have the time..... So I purchase a Crown XLS1502 amp for now.