I've (thankfully) thinned my IEM collection down in recent months.. so I don't have much to compare to.. my listening now is primarily with the T50RP Paradox & HD600 headphones. My 4.A custom is being worked on at Heir & the GR07 MKII is out on loan. The H-100 has few similarities to the 6X signature, so comparisons there aren't all that relevant.
I feel I've got a very good handle on what's neutral, balanced, warm, etc., so I'm comfortable evaluating it on its own terms. My source was the iPhone 4 (unamped), as well as with the Leckerton UHA-6 MKII & Objective 2.. I also used it with the UHA-6S MKII's DAC & the ODAC+O2.. and the Tube-DAC-11's DAC (and solid state output). All these are quite neutral, transparent, uncolored sources/amps, IME. All music used was well recorded/mastered from a variety of genres.
After letting my ears adjust to the 6X's fit (which was very good for the most part.. there could be some adjustments.. but nothing that seriously impacted sound quality/seal/insertion depth), the 6X' treble had a smooth overall character (in line with what seems to be the DreamEarz 'house sound/tuning'), but cymbals and snares were, respectively, splashy & lacked definition. Snares hits had a flat, 'washed out' quality to them.. cymbals sounded somewhat strident (alliteration, ma!). It felt like the upper & mid-treble were well controlled and articulated, but the lower treble/upper midrange was peaky. Again, I assure you fit wasn't an issue. I've owned a number of customs and am quite suer when the fit is off or affecting sound quality. The 6X' midrange was smooth, slightly warm, slightly thick, and dynamic.. it's really well done & the intimate midrange was quite engaging. What I wanted was a bit more openness & air. This isn't really a knock on the 6X as the midrange presentation felt accurate for the intended purposes (a stage monitor).. it just didn't align with my personal, subjective desire. The 6X' bass was excellent.. extended deep, was linear, fast, and textured quite naturally.. it reminded me of the UM Miracle's bass in some ways (though the Miracle's bass was more boosted, generally speaking).
Technically.. I felt the 6X delivered for the price.. but the slightly bright, mid-forward tuningwasn't exactly what I was looking for in terms of the signature.