In the X3, there is no such animal - it's a CID Controller (Radio); there is no boot mounted tuner module (unfortunately) and the CID Radio isn't the same as the BM series tuners - these are made by Becker whilst the CID Radio is made by Philips (well, the two I had were).

Also single tuner which is a real PITA as TMC is only 'live' whilst tuned to a TMC station (Classic in the UK) or when listening to a non-tuner source.

Re. the OP's original query, I don't think you can select any source other than the AV Audio when AV is routed via the TV tuner ... but perhaps with the VERY latest CID Radio you can (though mine is April 2007).