I have the rha 750's and the mee m6 pros. I really like them both. The m6 pro is "brighter", with less refined highs, IMO. Good sound stage and instrument separation. But they really are outstanding for <$50. They isolate very well, with the Complys I installed. That said, the 750's are better in pretty much every way. A warmer sound, slightly deeper bass, good clarity, wider soundstage, and instrument separation. I bought mine for $61 on Amazon as an open box. They were quite unimpressive for a long time, to the point I was wondering what to do with them...muddy, confused with complicated music (probably source music dependent), and just not quite right. But just recently they have opened up and sound very full. A good warm sound through either my iPhone 6+ with an e6 amp or my Fiio x3ii with the a3 amp. Good quality, excellent fit and sound. A better overall iem than the m6 pro...and I really like my m6 pros. The RHA's are very impressive now.
I liken the m6 pro to a Japanese hot hatch car...excellent fun to drive, but leaves you wondering what is above it...and that would be the 750's which to me are a Scottish kilt wearing single malt drinking gent driving an Aston Martin. They take getting used to, but are well worth it. Warm and dark, but inviting.
All of that said, I will probably purchase the Pinnacle P1's to replace the m6 pros. I will keep the 750's, though. I really, really like them. I hope this helps, and best of luck!
