The absolute best IEMs in that price range are probably Dunu DN-1000, which definitely sport that elevated treble of the Grado without the sibilance and even punchier bass. RHA MA750 would be my second choice
I ended up with the RHA MA750. Since most reports have the Dunu as having a bit more treble I think I made the right choice.
What I didn't realize was how far off the Shure E4 was from my ideal sound...the RHA 750 is almost like a shock. Where most consider it to be very smooth and if anything slightly subdued highs...I found them to have leaps and bounds more treble than the Shure. A few minutes in and I was extremely impressed.
I guess I had been trained to think IEMs just sounded "different". The RHA 750 sounds like real headphones. The Shure E4 is clinical and has a very forward and emphasized midrange...all about the vocals.
The RHA has far more impact, a more lively sound with far more extent on both the upper and lower end.
I would be blown away and ecstatic, but I am struggling a bit with fitment and isolation. The narrow E4 with a single balanced armature design and comply/black olive foam tips...the seal and isolation is exceptional, better than actual earplugs.
The RHA MA750 with a micro driver and shorter shaft just don't get in quite so deep. The provided foam tips are terrible, too stiff (uncomfortable) and don't soften or compress well with rolling. That leaves me with double flange or single silicone style. I know with my E4, neither style even came close to matching the comply foam.
So basically I am getting far better performance from the RHA in spite of less than ideal tip fitment. I ordered some sony Hybrids - if they don't do the trick I'll try complys (different size than the E4).