I like to alternate between the Elmar and the Summicron. Sometimes I shoot the same scene with both lenses, I'm trying to learn the differences. I find it interesting how I get different "looks" with those two lenses, but of course, they are completely different optical formulas.
I have them both, and I'm glad I do. Enjoy your Rigid Summicron.
I do see Elmars priced up to $600 on Ebay, I chose my auction carefully, had no competition, and won mine for $285. That's what I'd do, if I were you. But, as you say, there's nothing wrong with paying a -bit- more and getting the benefits of buying from a dealer.