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JimBA set averaging 5.7 sold for $255,000 in a Robert Edwards Auction about a year and a half ago. I would think one average a little over 4 would probably bring about 150k give or take a little. When you say everything but Wagner and Plank, I assume it will also not have a Doyle NY Nat'l, but will have a Magie error. If it has a Magie in a PSA 4, that could raise the value by 15-20k.
As it stands now, you are missing some of the most valuable cards, so I would not presume that 70% of the cards will equate with 70% of the value. Depending on what you have into it, it could be worth selling now. One by one would probably net more $, but not necessarily. Especially if you complete the set first, then there can be a premium on a nice set like that. Going with one of the big auction houses for a complete set would make sense.
JimB
http://www.robertedwardauctions.com/auction/2006/2.html
Edited to add link.