You should have bid on the E60 renntech on ebay if you can write it off for your business.

If you want a refined car go with the w124 500E. I think it is the best built out of your choices. I would try to get a more late model one. 1994 1995 e500 would be nice. Something with low miles or just had a lot of recient work done to it.

Id pick the 500e/e500.

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Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.