I used to have the Ultimate Ears Super.fi 5 Pro Earphones years ago. They were fine, though a bit clunky, and I had to replace the clear cable (the cable was clear but became progressively greener as it aged). They finally died after 7 years of constant gym use. I initially decided to get the Etymotic ER 4S because they're classics. But I decided to get the Hifiman RE-400 because of the good reviews it got on this website, especially in the 300+ IEM review section (due to the price/performance factor), and I was looking for a neutral IEM. But one thing that I was hoping I would not miss was the bass, because my UEs had fantastic bass and I really liked that when working out. I have an iPod touch, but found it clunky when working out, so got a SanDisk that's ultralight and just clips on. I decided to Rockbox it (I didn't want to Rockbox my IPod). I definitely trust Hifiman, because they have the best cans in the business. They're a heck of a lot smaller than my UEs and fit perfectly. When EQd by Rockbox, you couldn't convince me that the RE-400s weren't recommended for bassheads. Plenty of bass here. I think IEMs have really been getting progressively better in the last few years since I got my UEs.