Reading this and the manual, I've got to think that outside of the accessories they are really just the same machine with different software installed. The 600 accesses the higher frequencies in multi, so it has the capability, it is just limited from the single freq 20 and 40 by the software. Obviously the same with gold mode and the advanced settings that it is missing.
I thought I read something early on about the machines being able to update software. Would be interesting to see if a future software upgrade would be available (for a fee of course) for those that eventually wanted the extra settings, gold mode, etc. My 600 should be here tomorrow. Looking forward to getting out and seeing how it does this weekend.