I have driven quite a few Mercedes in the past couple of years. performance wise, my vote points to 300E. although I would like to test drive the other 124's to compare.(400e and 500e) I do think engine weight is a factor for handling characteristics in these cars.
drive safely!
adam

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320