Hidden Gems in Pre-Owned Solid State Power Amplifiers?

You need to not only look at their number, but the prices.

The deep discounts will tell you more about how frequently buyers tend to want to move them than how many were sold.

I like Parasound, in general, as a solid, neutral to warm piece of gear that looks great, and has great flexibility and very reliable. .

I bought a used Classe CAP-151 integrated to power my B&W CM9 S2 floor standers and i i love it! Plenty of power, a Balanced input, built like a tank and sounds fantastic. I paid about ~$800 for it and it worked well for a couple years but then an issue with the left side cutting out started. Turns out it needed a recap which set me back around ~$400 (14 in various sizes) but now it sounds better than ever.

I use it with a Mytek Brooklyn DAC upstream, anti-cables balanced, the rig sounds clean and punchy, the components have great synergy too.

I couldn't be happier considering the price of admission! You may want to factor the cost of a recap into your budget, an amp that is ~15 yo will likely need some maintenance. 

One incredibly refined integrated amplifier built in Italy and 
selling at under $2500 is a steal the Audia Flight Three S Integrated Amplifier it is very conservatively rated 100wpc into 8 ohms ,and over 160 into 4 ohms . My friend is driving his Big
Maggi 3-6 which are like 84 dB efficient , the current delivery on tap is hard to believe this $4k integrated can be bought for under $2500 is by far the most refined, powerfull and very natural weight 
I am strongly considering buying one ,for tube integrated the 
Ayon Scorpio at under $4k has not much competition for its sonics and build quality and 40 wpc and a  very powerfull 45 wpc in pure class A pentode with -0 negative feedback And constant microprocessor  tube monitoring 
and build is second to none using choke filtering power supplies 
pure gold plated berrillium copper tube sockets , these 2 products 
best in class stated around the world. 

N.E.W. Nirvana Electronic Works A20....sweet sounding class A amp