Thanks for the feedback dragon2knight.   I'm now leaning towards the R1s over the M4s... but also just put the Vsonic GR02 Bass Edition on my list as well after reading some positive comments on them. Tough choice! 

dragon2knight - thanks for the detailed review of the R1s.    I'm currently tossing up between the R1 and the M4 - one thing I'm looking for in my next pair of IEMs is some strong bass. How would the R1's bass presence compare to the M4? Anyone able to comment?   Any help in helping me...