Nice Khorns..I got my 81's in walnut from a friend's father 5 years ago for $1000. I am stunned how well they sound.
Regarding amps...Khorns are so incredibly efficient that you don't need much power for them to sing. They were originally designed back in the day of low power tube amps...so that is what I use to drive mine. I have a vintage Dynaco ST-70 and Dynaco PAS 2 preamp that have both been modified with upgraded boards and power supplies, using vintage tubes, and they make my Khorns just sing....fabulous midrange, deep, tight bass, beautiful, wide soundstage...and, best of all, I am probably only using 3-4 watts! The Dynaco is rated at 35 wpc (more like 30 realistically) so the amp is just above an idle. Vintage Dynaco gear is still very reasonably priced. You can find a ST-70/PAS2 or 3 setup for less than $500 if you shop carefully.
Best of luck...and have fun!