Looking at the packaging and the Trinity Hyperion in-ear headphones' build quality, its price is almost too good to be true.
Bass, midrange, and treble are all presented with an easy to listen to balance. At moderate listening volume the sound is warm and full, the soundstage is big and spacious, and the bass is a tad thick, but definitely not undernourished. Turning up the volume the sound grew harsh, and the bass thickened even more. The Hyperion is best enjoyed at more modest volume levels.
What's really lacking in the sound is transparency, but only in comparison to what you get from twice-as-expensive(US-only, $79) in-ears, my favorite under $100 in-ear headphone.
The Hyperion has a lot more bass, but it's much less clear sounding overall than the RE400. You miss a lot of detail with the Hyperion, but that might be a good thing if you're mostly listening to streaming audio or MP3s. One potential deal breaker for some buyers: Hyperion lacks a mic or phone controls.
Listening to well-recorded lossless files Hyperion sounded fine, and thanks to the extremely small ear pieces these headphones are super comfortable to wear for extended periods of time.
I also tried the next model up in the Trinity line, the Delta, but the sound was less clear than the Hyperion's. The Trinity Hyperion is sold in the US on Amazon, and direct from the Trinity website in the UK.