Going from the Adcom GFA 555 ii to the Bryston 4b SST or SST2?

The 3B SST2 has plenty of power for your speakers that are not a difficult load for an amp. 

@solartea123 Depending on your preamp/front end, it might be beneficial to upgrade further up the chain. What goes in, comes out. Just a thought.

Currently I use macbook -> apollo twin x -> adcom gfa 555 ii -> proacs. 

I’d consider doing something like this that’ll give you a better streamer, DAC, and preamp and then address the amp after that.  Right now I’d say the amp is the least of your worries  

https://www.amazon.com/Eversolo-DMP-A8-spectrums-Parametric-PCM768kHz/dp/B0CQX2X5HP