I had the same problem . IE42 occupied with 598 and HD621 so had to get ID20 ( 2 Toslink + 2 Coax ) for other sources . Really is a bit remiss of M not to clarify things for customers . We all know RJ45 input card is imminent now and this will free up IE42 again presumably ?
I could have held fire on the ID20 or even the IA45 before that but then I wouldn't have had access to Lossless for the last couple of years and I've just given up expecting any kind of meaningful roadmap from M anymore

And I've never heard whether my kit has been registered or not either !
Thank God the sound is immaculate though !

~M~