herewith is a short review of the HLSX (Magaosi) BK-50, with some relevant comparisons. i bought these for $35 from hck on ali.
viscerally, the BK50 impresses immediately with nice packaging and solid build quality--they look like a substantially more expensive iem. easy to drive, quite light and comfortable, though microphonics are significant. soundwise, i hear these as U-shaped, with voluminous, well controlled bass, mildly recessed but full-sounding mids and prominent, very well-extended highs. their overall character is warmish; they have the unusual quality of being very smooth without sacrificing microdetail. soundstage is large (wider than it is deep) and imaging/instrumental placement is very accurate. the BK50 is refined without sounding analytical or sterile. like the lz a2s, which they somewhat resemble, the BK50 sound great with mp3 and other lower quality files.
compared to the a2s, the BK50 have better treble extension and drive and present more detail; bass goes deeper but is not quite as fast and well-articulated on the BK50 as on the a2s. soundstage on the BK50 is larger and the BK50 sounds bigger overall.
compared to the shozy zero, which also have a warmish overall character, the BK50 are more energetic, with a less crowded soundstage and far better, more precise imaging. high end detail is similar.
the HLSX BK-35 have a slightly brighter, even more forward character than the BK50, with more prominent mids and more high end sizzle, though overall clarity and detail on the BK50 is superior. again, the BK50 has deeper bass, the larger soundstage and more accurate instrument placement. fans of a brighter, more energetic signature could prefer the BK35.
in contrast to the above, the XE800 is a completely different animal than the BK50--much brighter, more vivid and lifelike, with even more high end detail and a less colored sound overall. the BK50 has much more lowend presence and, especially, midbass texture; it is also a much larger, richer sounding phone. whether you prefer one to the other is dependent on your preference in sound signature.
in general, the BK-50 does not seem to be aimed at purists seeking a stage monitor; it is tuned for a more exciting, larger sound which is nonetheless very appealing if not wholly natural. the relative value of these is exceptional; for sheer enjoyment (if not accuracy) they are the rare beast that really does compete with the >$100 dunus, fidues, jvcs etc.