Ideally for bass get 3 drivers or more if you can. The other key element is fit. At your budget custom molds are out but there a lot of included and after market tips you can try and it’s worth to experiment to find the best fit for your ears. A good seal will really improve the low end response.
I’d like at Shure or Westone for quality earbuds in that price range and the more drivers the better.
The further you the chain you can stretch your budget the better the sound & quality only hurts once.
I LOVE the sound of my custom mol Westone IEM’s ($1,200) & I’m super bummed in the ultra rare occasion I’ve forgotten them or something stupid and have to use my $150 backup pair.
IEMs is one of those things where you really do get what you pay for and it keeps getting better the further you go. Diminishing returns at some point for sure but not until well after the $1,000 price point.