I don't have the RS1 but I have the HF2, for Grado sound. To my ear the HE-500 are more refined and even across the frequency range compared to the HF-2. They, the 500's, do not sound muffled in any way to me and that is not to say that you don't hear this but I am not sure why. I did find that for whatever reason the 500's take quite a bit of burn in and I never experienced this with the LCD-2 or the HE-6 as they took maybe a couple of hours.
Wow, the LCD-2 seem more full in the mids but the 500's are very neutral and clean. I will have to listen and compare more. The bass is stronger on the LCD-2 and in a way I like the more neutral bass of the 500's as the bass, mids and high frequencies tend to blend better but I really do like both.
So which is it? jamato08 says the LCD-2s mids are "more full", yet K3cT says the "LCD2 has a leaner, less forward but more transparent and nuanced midrange". Sorry, just looking for some clarification to these polar opposite opinions. I have never heard the HE-500, but I do own the HE-6 and find the LCD-2's mids more in line with jamato08's comments.