I personally love the M50's. They have a great sound its deep and warm, but not over-powering. I don't find it ever gets muddy or too pronounced.
I haven't really listened to many Sol Republic products, only one to be exact.. but I don't remember what model it was. I remember being surprised but I wasn't a fan, as you mentioned seemed a little to bass heavy.
Just my two cents. Hope I was but a little helpful.