As an alternative to the OEM unit, I'm looking at purchasing the Kenwood Excelon DNX9140. It seems to be a very nice unit. Does anyone by chance have this already?

 

I would guess that would totally depend on which features of the RER "uconnect with NAV" entertainment system you believe are most important.

The RER has NAV + CD/DVD + HardDisk MP3 Storage/Player + USB + AM/FM + Sirius SAT + Aux + Steering Wheel Controls + Bluetooth Hands-Free with Voice Recognition as standard (with iPod Controller + Back-Seat Video + Rearview Camera as add-ons).
The Kenwood has several of these same features, but NOT the Disk-based MP3 Storage/Player. And several of the RER standard-features are extra-cost add-ins for the Kenwood (Sirius SAT and Steering Wheel Controls and USB and AUX input - as well as the iPod and other features that are add-in for both units).
Beyond that, there are likely several of the interface and software features that each unit does better than the other (but you'd have to learn the quirks of each to tell which you like / dislike).
Does this help ?? Or extend the quandry ??