From what I've read here, there is a world of difference between the W124 (which you drive) and the W210 which you are contemplating, the W210 is the first of the E class on a downward slide of build quality that began plaguing Mercedes in the late/mid nineties.
Read the "Spring Perch Failure" thread on tech forum for starters.
These cars are very nice to drive when all is right with them, and they are very roomy too, but the quality just isn't there like it was in the earlier cars.
If you must have one, check it carefully for rust, books and records, and a PPI by a good Mercedes mechanic is essential.
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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)