I have 5 sets of AR-9's. From my original bought-new in 1982 pair to a set rebuilt by an electrical engineer (best sounding of the 5). Rebuilt set is on my secondary stereo system. 3 sets are on my HT setup.
IMHO they are some of the best sounding speakers I have heard (that I can tell... to really tell, need to do A/B comparison in same room with same equipment). I A/B'ed with rebuilt Dahlquist DQ-10's I bought, and the rebuilt AR-9's were better in every way.
I used to drive them with big Yamaha amps, but have been driving with 24 watt Canary tube amps... and they sound wonderful.
Note: I don't hear above 14k hz. My main system now has Quintessence Acoustics Summit speakers built/bought in 2010. Though the bass is better/tighter in the Summits, the rest seems the same as the rebuilt AR-9's... which is great.
Most AR-9s are going for $1200 a pair and my need new surrounds on the speakers. Spending several hundred more and having rebuilt/new wire/bypass switches/etc gives you one great bargain, especially at the prices of speakers today.