If you’re looking for a fun IEM with sound technical foundations that you can listen to for hours at times without any fatigue, then the FIBAE4 is definitely a must own in a collection especially in its price bracket! If you’re looking for fun tuning with more bite and a snappier attack then there are a few mid range IEM that could suit you more like say Earsonics Velvet v2 or - more pricey - the Earsonics Purple or Campfire’s Atlas.
If you’re looking for a smooth and fun sounding IEM with strong bass, beautiful mids and lively treble that does not compromise on fundamentals and is showing top performance in their price bracket, the U2 is definitely worth an audition! There are few gems in the sub 500$ range and the U2 is one of them in my book.
If you’re looking for a neutral IEM with top notch detail retrieval, great soundstage and accurate tone that provides a fatigue free experience without breaking the bank then the U9 is definitely an IEM you should try! If you’re looking for more bass kick, sweeter mids and sparkle, then other IEMs of the StealhSonics will be of interest.