I bought a Topping A50s a while back to drive my Anandas with the expectation that they would probably also work OK with the Arya when I upgraded as it seemed like they would have plenty of power balanced to drive them.
I got my Arya in and they definitely got PLENTY loud with the A50s...everything sounded really good! However, back in May, I decided to buy a Jotunheim 2 to pair with the Bifrost 2 I had been using. I really just bought the Jotunheim so that I could have a proper 'stack' that looked nice and really didn't expect to hear much difference in them as the A50s was touted to sound almost exactly like the A90, but wasn't able to deliver the power of the A90. Since the A90 gets RAVE reviews from Joshua Valour and so many others, I figured I had found the 'sweet spot'.
Well, after 3.5 months I FINALLY got the Jotunheim delivered. After listening for 30 minutes, I couldn't believe how much better it sounded than the Topping. _IF_ the A50s truly sounds just like the A90, I have a hard time believing anyone who has heard a Singxer or Jotunheim 2 could recommend it over those offerings.
I won't say the Topping sounded _BAD_, because I was truly happy with it! I did find myself sometimes switching to an EQ profile to add a little bass, but thought things sounded good. Now that I have the Jotunheim, when I plug in the A50s, I immediately notice how 'compressed' everything is. There's still plenty of soundstage, but the Jotunheim really adds some space and brings out the best in everything. Also, I don't feel the need to do ANY EQ now...