I'd say just slow down a little. And stay with the facts. You mention I think in your first post that your old starter turned that engine to 1000/1500 rpm's. If that is what it read, then your tack is obviously out of whack. I am guessing now, for I don't have the exact number but I think if a starter can crank that engine up to anything over 200 RPM, it would be a very good job. About 700 rpm is ideling speed.
You talk about an extra battery and solenoids ect, are you sure this extra junk isn't crippling your starter. Mercedes Engineering thinks a single battery of a rather large size, (in cold cranking amps) is sufficient for the job. I would suggest you do a real good job of testing out your battery and starter. You wouldn't be the first that got a rebuilt starter that was less then good. Have them test it. It is possible they will give you a new one.
Have you checked your valves? A bad adjustment there can make starting mighty difficult. Do you have a block heater? Have you been using it? Have you checked for fuel system at all? Have you replaced any of the fuel filters? All of the above can effect cold weather starting very much.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!