The E series is a good IEM series especially the E70 but the entire earphone assembly is shaped funny. the leg is a bit short so if the tip does not fit perfectly, the sound is badly affected. As it was a demo piece, I did not press the stockist sales rep to fit me up with the exact tip. So i pressed it into my ear and helped it stay in place with my fingers. Not ideal!. Still I reckon the bass even for the E70 is set as flat or neutral. If there is bassy noise in the environment ( for my daily train and bus rides) the sound won't be good enough. So it is for "Monitoring use".
To your question, I have used the CKS 90, ( that I call the traditional Audio technica sound) - Grew out of it.
Tested the IM series extensively when I was in Japan over 2 holiday trips. - ie IM01, IM02, IM03 and recently at the Spore AT Stockist the IM04
Also tested the IM70, IM50 in Japan extensively.
Surprising even as I was willing to pay more for the IM02 or IM03, their sound signature did not suit my taste
I found the IM70 and IM50 suits my music more (which is Jazz - all sub-genres, Blues, Blue Grass, Country, Classic Rock, Audiophile HD Track and DSD64, DSD128)
So anything from FourPlay, Chris Botti, Herbie Hancock, Eric Clapton, Alison Krauss and her band, Miles Davies, Chesky label downloads, etc)
I would recommend you try out the IM50 and IM70.IM50 is bassy and a bit bloated with leak through to the lower mids. But it is a fun IEM.
I came upon the BKS77 as it was offered as a store special by BIG Hifi chain store in Tokyo - i think it is an adaptation of the iM50 with tuning done specially for BIG, Flatter bass - but still good and with impact, flatter mids, and slightly more refined treble. I swopped the cable (with the stupid Iphone microphone) with a better 6n OCC cable - sounds so much more refined and clear)
So I bought the IM50 and the BKS77.
IM70 is more balanced. Try that and if you cannot try before you buy, stick with the IM50 - you can always download the iAudiogate music player which has a very good neutral sound, transparent (it can do up to 24/192kHz as well as DSD64, and DSD128 if you have a matching DAC - I use the iDSD Micro with the Canon camera kit and Apple 6plus to upconvert to higher than 44.1 or 48 and up to DSD)
The above is of course for my tastes. I don't think you can find the BKS77 outside of Japan but IM50 is not expensive so go for it. Or by the way I struggled with the Logitech UE-900 for a entire year, Just could not get the sound signature to suit my tastes and then the plastic case came apart at the joint. Piece of US400 Crap!
Audio Technica is not audio jewelry like many other audiophile brands but is rugged well built and sounds 'commercially pleasant'.
I leave my serious listening to my Senn HD800 and Hifi man HE560 on my home set.
Have fun
Kelvin