Hi Woollyjoe,
I have used the Sennheiser dongles, both USB and the iPod one, and have been very pleased with the sound qulity of both of them. I have not been able to do a comparison with the Creative one.
I am somewhat surprised that you say the code for an APT-X enabled QBD76 is 1234. On the Chordette Gem its the reverse. 1234 is non APT-X and 0000 is APT-X enabled.
When you use either the USB or iPod dongle, you are NOT promoted for a code, it does the handshake with 0000 automatically. At least on a Win7 PC it does not ask for a code with the Sennheiser USB dongle.
Did you check with Chord the code used for the APT-X enabled QBD76.
I am a little concerned you will find the dongle and QBD76 will not talk to each other. I had precisely this problem with the first non APT-X enabled Gem I had.
Regards, Peter