I use my IE8s when I travel so I like music that keeps me on the move, i.e. involving beats and mainstream music, but when I'm home, it doesn't necessarily have to be that; though I still listen to it.
with the k702 it's a different perspective, and I can listen to chillout music so it kinda compliments each other.
At the end of the day, the IE8s for me were based on informed research upon reading the forums and deciding what would be best; I like the fact that I can tune the bass to what I require and the detachable cord which is very very useful in the case that the cable dies on me. I haven't experienced many other top tier universal IEMs, but I'm happy with what I have and I'm enjoying the music a whole lot. I've tried the JH's and honestly, I'll go down that line when I have a bit more to spare, but when I tested it out, I found it a tad too revealing and on the move, music quality is not the biggest thing; would love to own it, but I don't have the finances nor do I require it at this point.
that being said, the IE8s are short on SQ either. to answer your question on the IE8s, well, I got them when they were still 390 AUD here before they shot up above 550 AUD so they were cheaper than all the alternatives e.g. Westone 3s, etc. I was never a big fan of Logitech, so UE was never much of an option. MTCs didn't get much time on the boards here at the time I was looking into phones.
I'm a casual listener, but I love my music and as long as I'm happy, I don't see the need to spend another few hundred to 'test' another pair of phones.