I have the Truthear Zero and also Moondrop Kato, JVC HA-FDX1 and a few others. For me the reason to buy another IEM would be to get smaller size, better fit and isolation. In the past I've owned Massdrop Plus Universal and Vsonic GR07BE and, using different approaches, they both had much better fit and isolation that any of these *enormous* Moondrop and Campfire and Truthear type designs. The Massdrop was 3D printed and brilliantly designed to conform to human physiology and, despite 3 BA drivers per side, was rather slim. It felt like a custom IEM, absolutely perfectly sitting in the ear and achieving very good isolation without being deep fit. The Vsonic had swiveling/rotating nozzles (a slightly different way to the JVC method, and a bit better in use) and this alone let the thing sit absolutely perfectly in your ear. Again, not a very deep fit but really great isolation and comfort. Unfortunately Massdrop & Vsonic have the component quality and manufacturing QA of a drunk and almost everything they make seems to be cursed to die young. I've had 7 pairs of Massdrop IEMs fail (3 x Massdrop Plus, 2 x EDC3, 2 x Pinnacle PX), and 4 Vsonics (3 x GR07, 1 x VSD1S) - yes I got a lot of refunds and replacements! Meanwhile I have some Sennheiser CX95 well over a decade old which now look like shit but just won't die. And Shures go on forever. I hope the Truthears and Katos and JVC go on a long time but it is nice to know that now several manufacturers are making cheap IEMs which sound fine. It used to be an expensive nightmare finding replacements but right now I could confidently pick 4 or 5 IEMs from $50 to $200 and know I'll like the sound. I wouldn't love the bulk and fit though.