Whew...that is one sweet setup
Have you tried it through a low powered DAP alone, such as a phone, clip, or laptop? I don't have much evidence backing this, but every true dynamic driver IEM I have used in the past (I say true, because shure se215's piddly little microdriver with no sub bass doesnt count) sounds best through a source like the clip. Examples include Klipsch s4, Meelectronics M6 Pro, Sony Xb50s, TTPod T1Es, and these T10s. Only higher end BA I used was westone W3, and those sounded better with amp, but they were still not exciting enough.
I don't have much experience with high end equipment such as yours (X5 and vacuum amp?!), so hopefully someone who has similar equipment can comment. I would say, try it out of a pure, weak source first with wider bore eartips, and hope for the best! I hope it works, so you don't have to go through that returning hassle.
I am really curioud though, something about the samsung s5 stock eartips makes it sound quite unlike any of the other eartips, in terms of detail and energy. Sony hybrids, stock double flanges, and random ones all seem to change the sound marginally, but the s5 eartips change it by a little bit more. Not sure where I am going with that, but good luck!