Installed latest 46.1.1049 update and got some time to tinker around on my A600GS.
Same as SkulleateR I have to report that latest 5.8.7 Amiberry does not sort out the speed issues on the A600GS, e.g.
Jim Power ... unbearably slow
ReshootR ... unbearably slow
XTReme Racing AGA v2.0 ... unbearably slow
Reshoot Proxima 3 ... 1st level ok, slowdown in other levels but still playable
What has improved with 5.8.7 is stability. E.g. XTReme Racing AGA v2.0 crashed Amiberry 5.7.5 after a few minutes of play (at most). Now with 5.8.7 I was able to complete a full season without crashing. That is with JIT off, with JIT enabled it still crashes rather quickly.