(Note my impressions are subjective with no DBT testing done).
I haven't heard the a9010 so I don't know how it compares. I have heard the A-100. I use it primarily as a headphone amp where it sounds fantasticwith my HD600's and HD700's, just throwing them around really. Only drawback for headphone listening is that depending on the headphones when you drive them with the resistor bypassed (non stock mode), there may be some slightly audible hiss (not for speakers).
I have previously used it to power Axiom m80 towers which it did without breaking a sweat and pushed them to lifelike volumes with nice imaging and a stable top to bottom sound without sounding weak in any area. I've performed side by side comparisons with it vs Crown XLS amplifiers, large old school crown amplifiers (250 watts per channel class AB), and the Emotiva XPA-2 gen 1. It sounded better to me than the Crown XLS which appeared to have a upper bass suckout with my towers, was more pleasant than the old crown and had a similar tonality to the XPA-2 gen 1 - though the XPA-2 is a better amp imo.
Have also used it to power large book shelf speakers. For comparison I use the Emotiva XPA-1 gen 2 monoblocks to power the Axiom M80s normally.
Based on my subjective experience, I recommend it.