You might be interested in knowing that I have made an open hardware RAM expansion for the A600 similar to PeteAU's for the 500. It uses SOJ-40 RAM and is chip RAM only, with optional RTC.
It's an open design, the project is on github:
https://github.com/SukkoPera/OpenAmiga600RamExpansion
I am also selling PCBs and component kits on AmiBay:
http://www.amibay.com/showthread.php...ion-with-Clock
On my github repo you will find more open hardware for the Amiga,
C64 and C16. More stuff will be released soon. Enjoy!