I used to own the marshmallows a long time ago so going by memory they were pretty good for their price at the time. I haven't heard the soundmagics so I can't comment on those.
I haven't heard the following in ears personally but they seem to have gotten a lot of good reviews on this forum so you might want to look into them:
JVC FX67 ($18 on amazon.com) http://www.head-fi.org/forum/thread/553590/fx67-review-a-hidden-gem
Meelec M6 (if you can wait it out they come on sale here and there for under $15) http://www.head-fi.org/forum/thread/453242/meelectronics-m6-review
Also check out |joker|'s thread which is tremendously helpful: http://www.head-fi.org/forum/thread/478568/multi-iem-review-188-iems-compared-dunu-dn-12-trident-dn-16-hephaes-added-8-10
I just bought a pair of FX67s and they are shockingly good - I like them more than my Ety HF5s.
Re. joker's thread, I appreciate the absoluetly epic effort, but in my limited experience it can be misleading. I'm not the only person to think the HF5s and FX67s are much closer in sound quality than he rates them, and as for claim that the HF5's microphonics are low - well, either the custom fitted tips he was using made such a large difference that his review has nothing to with a stock HF5, or comparing even the simplest detail of IEMs is so subjective that reviews are worthless, or a LOT of people are wrong!
I can't comment on the Soundmagics, because I haven't tried them, but the 67s are a very safe bet.