I haven't heard the Soundmagic E10, but I have been spending quite a bit of time with the RHA MA350 over the past few months. It is easily one of the best sub-$100 IEMs I've ever heard. My detailed review will be up shortly, but here's a quick run-down if it will help...
The bass is nicely weighted, with a very smooth extension into the sub-bass region. It seems to maintain a good balance between warmth and responsiveness, without ever being too thick. Mids are unexpectedly articulate and NOT recessed into the nether regions as one would expect of typical street/fashion IEMs.
Upper mids are crisp and truly shine in terms of offering a nice snap, particularly for acoustic percussion. Occasionally, there is a bit of a steely harshness in the mids (especially towards the upper mids), but its not high enough in the frequency range as to contribute any sibilance (which is a good thing in my book). Highs are quite clean with a gradual and smooth tapering - not a sudden roll-off - and complete the picture with "just enough" sparkle (but not a lot of airyness).
Overall, the signature is balanced enough (although not flat), with mild emphasis in the mid-bass and upper-mids for a fun, engaging, and lively experience. I also quite like the soundstage, which had nice width, reasonable depth, a just a bit of height as to not feel stifling.
Just about the only drawback that bothers me is how microphonic the cord is. Bit noisier than most actually, but I mitigate that with the slider, and simply by wearing them over the ear.
I would highly recommend these, without hesitation.
BTW, I think their giveaway is still active (http://www.rha-audio.com/us/competitions
), maybe you can try your luck at winning one?