Michel, sad to see the car back on the market again ! Sad, because if it leaves your ownership, it will be like drawing a line to close a chapter that's been developed and cherished for about six years. I mean, you have sold the blue 450SEL, and that ostensibly may have freed up some space for you.
6.9s are up in value, other than some of the crappy ones that come on the market. Yours will be no different - it will increase in value. 6.9s can still be reasonably inexpensive to maintain without all complications of mechanicals and electricals. Owning a 6.9 should be all about pride of ownership, appreciation of the product, and the realization that there may still be fututre expenses - but a lot of these expenses have already been met and have been amortized. Remember, there is no other car like a 6.9, faults, warts and all.
So, why not consider keeping the car ? Put it on Club Plates, if you will, and also attend to some of the issues you may still have with the car, one by one ? Take your time, work on a schedule of repairs, maintenance, beautification, reasonably secure in the knowledge that the Red Terror will actiually increase in value - you still have time, also look at prices being asked for 6.3s, to some degree and in certain areas inferior to the 6.9s, and start to realize that you may actually have an asset on your hands, and not a liability. Anyway, enough of my ramblings. Regards Styria