Your ACAtune command line should work fine. Those color changes doesn't look like anything the ACA should be able to cause, but I could be wrong. Is the A600 100% fine without the ACA installed (or when disabled)?.
It is normal that you see many memory regions in MBRtest since the ACA620 fills out all the small unused memory spaces to optimize the amount of available memory, even though some of the blocks are rather small.
Also enable the testing of chipmem in MBRtest (the top one) since that communication is fully happening through the CPU socket where as fast mem access is handled locally on the ACA. You will see some flickering on the screen as the test passes through the visible screen area but this is normal and no persistent gfx corruption should happen (like it did on my 600 when it wasn't stable).
I'd try to clean the CPU thoroughly again, reinstall the ACA620 and see if it helps.
Is your board rev. 2? It should be, but if you got a rev. 1 by mistake, then you won't get it to work.
Last edited by demolition; 23 June 2013 at 00:15.
Reason: Removed part with old caps as they were replaced :)