MS-1 are great with all kinds of music. They shine with acoustic, soft rock type even more. As you can see in my signature, I also own the RX700. They have good isolation when I need it and more bass compared to the Alessandro. The sound quality isn't bad, it's just not on the same level as the MS-1. But if you consider the price to performance ratio, the RX700 is a great value.
You're either going to love it or hate it when you upgrade. I can suggest a cheaper approach: try out the KSC75, I had them before every other headphone I own (MS-1 included). The Koss are similar in sound signature to the MS-1. That way, you can figure out if you should switch to these particular headphones. Or, if you've got the cash and itching for instant gratification, then go ahead and buy the MS-1. Their resale value is pretty good, so you can always get your money back.
Hope that helps.