How much is the Panasonic 14-45mm worth vs. the 14-42

I just ordered my first m43, the g5, which should be here on Thursday! Can't wait. I got it for $499 with 14-42mm and the 45-150mm for only $99 more, so very excited. From what I've read (And that's been alot lately!), I want to sell the 14-42mm and buy a 14-45mm.  From what I've seen, I should be able to sell the 14-42mm for somewhere around $80 on Ebay. How much would you suggest my max limit being on the 14-45mm to make the upgrade worth while? Thanks