Yes, the MS-Pro is pretty kickass for metal beleive it or not.
I went straight from the SR60/MS1 to RS1i a few weeks ago (I have owned the SR60s since 2007, and the MS1s since 2011). It is most definitely an upgrade... more accurate, but also more refined than the SR60 (which I still do love and am hanging on to).
It's definitely worth it, you can even buy mine
RS1i and PS500 sound very different.
The PS500 has more rolled off highs compared to the RS1, and has a more elevated mid bass as well. This gives more weight to stuff like pop and some fun bassy genres, but sacrifices the elevated treble/upper mid that Grado's like the SR60 and RS1 have.
Not sure what Sennheiser you have, many of the models have very dull treble. Especially in comparison to Grado's which go above neutral.
Best to see if you can hear them first, if possible.
Well, compared to the SR60 they are accurate...
The RS2i has its fans, and I can't say for certain that it was worth the $220 difference to have the RS1i, but at the same time I knew that I would have that voice in my ear telling me I should have tried the RS1s. I figured that bit of cash bought me some peace of mind.
totally agree with you! SR60i have a very fun sound not as in bass but the mids...VIVID <3 xD