I can't take it.
Prolly your best place to do this would be right here at our very own little Jemsite community. *Put up your UV on the buy/sell page (for UV's and JEM's, not in the forum) and decide what difference you are willing to pay. *Then make the deal, UV777BK + $???? for trade. *You might be surprised at what you find. *If that doesn't work, there are JEM7VWH's on ebay regularily, you can always privately sell your UV and e-buy a JEM. *Personally, I'd wait, put the $$$'s together and buy a JEM and keep the UV if at all possible, I think you'd have some regret selling your UV at some point.
Just my $.02