I payed around $600 for the -114, but the latest TCU -798 is around $1300 (actually realoem has it listed for even more) for some reason. I've no idea why they put the price up since its pretty much the same thing !!

I put together as much info as I could on the BT/Assist TCU parts:

09/2004 - 02/2005 84116946993 1st release of integrated BT/Assist TCU. No voice input, however can be added by seperate SES voice module.
03/2005 - 05/2005 84106964114 Added support for voice input (phone only). Added support for Siemens S66 phone
06/2005 - 08/2005 84106965056 Improved performance of Address book transfer on some phones reported.
09/2005 - now 84106963798 Fixed problem of NAV defaulting to Telephone menu on startup.