If you are going to have one, be aware the upkeep WILL cost plenty, make sure all the electronics, and the climate control work perfectly, in addition to all the usual caveats for any used Mercedes. thw W140 is a very regal, imposing and stately ride. Very safe too.
The '99 "Grand Edition" (only 600 made) all of them in Obsidian Black, with the 500 engine and factory AMG wheels, special bird's eye maple trim and other exclusive upgrades, would be, IMO, the most desirable one to find buy and keep.
__________________
1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...
1995 E 420, 170k "The Red Plum" (sold)
2015 BMW 535i xdrive awd
Stage 1 DINAN, 6k, <----364 hp
1967 Mercury Cougar, 49k
2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive
(sold)