I would recommend the Audiosense T800. It retails ~ $298 USE and is my end game all BA set (8 knowles BA). Low impedance, easily drivable from smartphone, but will benefit from DAC/AMP to scale better. Good at all music genres.
Audiosense T800 excels at clarity, details, instrument separation, soundstage. For a BA bass, it has a bass that sounds like a DD due to its vented subwoofer and tuning, extends very low in the subbass. Isolation ~ 30 dB, the best I have so far in my IEMs, I use it for stage monitoring exclusively. It is a bit bright, but the treble can be tamed with knowles filters or eartip/cable changes if u are treble sensitive. Truly the cliche that you can hear new details in music that u have heard for ages is true when I put on the Audiosense T800.
Some headfiers in the Audiosense thread say the T800 can hit 80 - 90% sound quality of the Campfire Andromeda, at a fraction of the price, I can't say for sure as I haven't heard the latter, but that is amazing for the coin. But it definitely blows some of my midfi multi driver westones out of the water, and at a cheaper pricing then them.
I've been using IEMs for the past 15 years for stage monitoring and music listening and I can honestly say the CHIFI IEMs have caught up to the western budget to midfi IEMs in the past 2 years. If u are not brand conscious there are good CHIFI IEMs that excel at price to performance ratio. IMHO $50 - 100 USD can get u some great sound nowadays, so your $300 budget is way more than adequate to get a good midfi set.
If u are looking for cheaper stuff, there are a lot of good CHIFI fare that are < $50 USD with great reviews that were recently released: TRN V90, KZ ZSX, CCA C12, BLON BL-03. U can check out or ask more at these threads:
https://www.head-fi.org/threads/bes...nd-impressions-sharing-reference-list.805930/
https://www.head-fi.org/threads/bes...ith-reference-list-no-big-brands-here.872245/
https://www.head-fi.org/threads/chinese-asian-brand-iem-info-thread.820747/
All the best and hope u find what u are looking for!