Baseboard Plus 1
 

Will work the 1 Meg Expansion Baseboard Plus 1 for the A500+ with the A600?

No.

The A600 uses a completely different expansion slot... A500 and A500+ share expansion schems, but not the 600. you will need a special A600 RAM expansion board. Shouldn't be too expensive nor hard to come by, I got mine for 30 bucks and that was quite a lot perhaps.

The in-built battery backed-up clock is handy :)