While the 5-speed may be more appealing to an "enthusiast" it's still stuck in a 300E, engine and body. So, while there's a chance for a premium over an auto 300E, it's not going to double the value, etc. Time has shown that, except for the limited production uber sedans, it is the SL's that seem to rebound in value, approximately at their 30th anniversary. So, you '70's SL owners with good condition cars . . . it might be your time.