I recieved the DIY MX500 2 days ago, and here are my quick impressions:
They sound completely off. No pinnea gain there, and there's an important deep at 6k which doesn't help (and I can't get it EQed so it's a major issue). But admittedly tehy sound "fast" and have a very enjoyable response in the lower part of the spectrum. They seem to perform best with a somewhat loose seal, where the bass are linear (but still extanded) and distortion free.
I'd love to know about cheap buds tuned with a pinnea gain if you guys have suggestions (many thanks to
@cenizas who did it already). So far I have MS16, Openheart and Ty 32 as winners in my book (all well worth their low price if you don't have them yet)