Interesting Scuba Devils, as I am thinking about buying another IEM soon - either a Xelento 2 or a Thieaudio Prestige or maybe a Fatfreq MSE - in order to have another, even more detailed flavour besides my IE900.
As you seem to own the IE900 as well as the Xelento 2 and already had the opportunity to listen to a Prestige could you maybe elaborate a bit about their strengths/weaknesses in comparison? Which one of the three mentioned (that you know) would you keep if you were only allowed 2? Do the IE900 and Xelento 2 differ enough to own both or are they quite close to each other?
I definitely couldn't comment on Prestige in as far as if it would be one I'd keep over the other two - for two reasons: I didn't try it for long enough, and I more often than not gravitate back to single DDs... I like a selection of 'specialist' DDs for various genres and listening scenarios, and for the most part any hybrids I buy don't last long in my collection, with the exception of Fir Audio KR5 as I find that quite unique.
Off the top of my head, I would say X2 is more flexible for my library - I can play absolutely any genre, and they sound at least very good, and often excellent - plus incredibly small, and comfortable, so my top choice when travelling with work etc. I find IE900 more impressive with specific genres, especially from a sub bass to treble balance perspective - mostly more energetic electronic genres. Is it worth owning both? - I guess that depends on what you feel you might like to change or improve on IE900... they are relatively similar, definitely not significantly different - I've recently purchased the Victor/JVC FW10000, and that is an incredibly different set to both, but I find it more of a specialist with very specific genres - in those cases, I'd take it over either X2 or IE900 any day of the week... likewise the Turii Ti, not an all-rounder, but amazing with some genres, and my personal favourite IEM.
X2 has become my go-to DD for easy listening, in any scenario, with any genre - a fantastic all-rounder in every sense... works with any genre, very comfortable, light, good isolation (depending on tips of course), and easy to drive... I love them with my Lotoo Paw 6000 as a great portable solution.
I'll choose IE900 if I want an excellent session with genres like techno, D&B, IDM, to name a few - and often still grab it over X2 when going for a walk - I guess it's more exciting to my ears at least.
Sorry, that probably adds more confusion as opposed to helping!