Hi Jensen,
Here is my experience. I have 2 ACA amps configured in mono driving my Pi 4s with JBL woofers and B&C 250 tweeters. Contrary to what Tom stated above, my ACA monos can drive my Pi 4s brilliantly. I listen around 80-85 db 8 feet from my Pis. There is no loss in dynamics and I can drive the Pis louder if I wanted.
However, I also built an Aleph J and an M2x Pass amps. These 2 amps sounded different on the Pis. Better than the ACA? Definitely, but they are also bigger amps with 25 watts power per channel.
I think you will enjoy the ACA in your Pis if you will build them. You absolutely need to configure them as monos (bridged or parallel). If ever, try building the ACA amps with premium parts. In my ears, the ACA amps with premium parts sounds way better than the ordinary ones.