yeah the whole 'in-your-head' feeling of IEMs can be hit or miss depending on what you like. unless it's some uber IEM like JH-13, I think a fullsized headphone is going to give you better soundstage and more comfort.
Some people just don't like sticking the foam into their earholes, that might be an issue as well. Isolation is nice for commuting and such, but if you are gaming at home it becomes a moot point.
CX300s are quite nice for what they cost though, good enough for general use.
I never got to try those JVCs but heard very good things about them. My personal pick (among those that I have tried) would be PX-100. Very fun and non-fatiguing sound, quite comfy, foldable and does not require amping.
Haven't kept up with the similarly designed newer phones like PX-100 II or HD238... are those any good?