Of note, certain revision A600's can be fussy with addons like the A604 and ACA620, i am not sure about the A604n though.
I have the A604+Aca620 but when i use them both on my rev 2D A600 i get instability issues, i ended up reverting back to my original trapdoor ram+Aca620 in which works fine together.
Unfortunately my Indi Ecs is unusable and sitting in a box as it needs the A604 to work, as apparently Rev 2D A600's suck.
Edit- Some more info about this can be found here-
http://eab.abime.net/showthread.php?...evision&page=4