After spending some more time with the Stage 3 and Stage 4, I can say for certain that these are truly nice iems.
The Stage 3 is more on the neutral side, and thus very versatile. It sounds good with everything I would say, because all frequencies are well balanced. I will not be getting one however because I am sometimes not engaged into the music with them. I think I just do not like neutral iems that much. Other things I noticed is that the subbass is not sufficient to me, compared to iems like the SE5 or the Stage 4. So a great all rounder but I think I want something with more flavor.
Now the Stage 4...really difficult for me. I really like this iem. Great bass and punch with it being overwhelming or fatiguing like it can be on the Fitear 335. The mids are fluid and engaging and the high are smooth but still quite sparkly and extended. It is like a Stage 3, but performing better and more engaging to my ears. Another thing that the Stage 3 lacked a bit and is improved in the Stage 4 is soundstage depth. Right now I am considering whether I should get this custom or not. I will also wait for some friends to compare with customs I have not heard and am considering (such as the 435). Also, these demos are really not comfortable, and I hope the custom version will improve this as well as widden the soundstage a bit (not narrow by any means, but could be even wider).
I am passing these on to spkrs01 and the rest of the crew for more impressions !