You’re welcome! Thanks for reading!
The MSR7 sounds nigh-identical to the SR5 as they use the same drivers and the same tuning, so the only benefit you’d be getting is the additional comfort of the over-ear fit. When I compared them directly I was impressed at how close the sound of the smaller headphone came to the bigger one…but you’re not going to see much difference there.
I think that both the M40X and the 7506 sound more like what you’re looking for. If you’re not worried about portability, I’d probably pick the 7506. It’s the more detail-focused of the two, it’s usually cheaper, and it’s a very analytical headphone in general that still has a surprising amount of bass richness. It also sounds different enough to your SR5’s that it’ll be a better counterpart.
Hope that helps you out!