Just one question regarding 568.2mm; How old is that unit now? Should I be concerned with reliability and/or repair ?
The 500 series processors and analogue items are extremely reliable workhorses. Not much to go wrong with them. The G Series processors and 800 series units have never enjoyed the same PSU reliability as the 500 series with their Linear Power Supplies (rather than switch mode). I'd suggest that a 568.2mm is likely to outlast a G processor on that front before needing any service work, even if you were to make your choice from what's available on the market right now.
You also have the considerable benefit of Marc Koval, formerly of Meridian US, who now provides service work for out of warranty items should it be needed.
Cheers
George
PS the link at the top of the page to Duncan's Meridian Info will let you browse a huge archive of data sheets and reviews on the products.