Let me share my experince abt the dension, its a good device that helps you to connect audio to your stock HU, for E60/E61 no issue its plug and play, basically in the I drive u will see instead of CDC 1-6, u will see in addition 7 ipod, 8 aux n etc.
CD 1
CD 2
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CD 7 Ipod
CD 8 etc
I tried connecting for my 730E65FL but the dension that they had was not compatible, the latest dension carries the software for the E65, E90 etc. I will be fixing in a couple of week.
As for warranty u need to switch of the Dension when u send for servicingso that there will be no error reading. I think there shd be no issues with the warranty unless it is a matter that concerns the changer. No cutting of wires just re feeding the optic fibre thru the dension.
You can also connect the IPOD, USB for mass storage, Aux in. You can also add bluetooth function for Handphone, and video input for IPOD.
I will post the pics once i manage to add the dension. cheers