I've never heard of the RS-2 but i've got the RS-1. I've tried listening to my RS-1 a little while ago with some Rammstein and other heavy metal. I found that the phone lacks some weight on the bass strings, basically around the mid bass region. Hence, the RS-1 sounds rather "clean" but on some music they sound a little "raw". Not sure if that's something you are looking for. The RS-2 is a little warmer I believe.
I bought the RS-1 on a whim as I found that it does some music darn well, I was sold by the RS-1 + Hotel California (i dont mind keeping a phone just for that track
) It's a great compliment to my K701.
The K701 does all kinds of music for me, though being a variation of the hd6x0/dt880, the K701 sorta hit my sweetspot for this kind of sound signature. The 650 totally didn't do rock for me, the bass was phat and slow and the treble roll-off just made rock musics lack the "oohmmmpp". The k701's bass is faster and punchier than the 650 though it doesn't seem to hit as deep but it's not by a very large margin. The k701 is also not as laid back as the 650, vocal is smooth and upfront, slightly lusher than what I'd like but with the proper source and amp one could tune it to fit your taste. With the PPA and 1212m, I find the vocal on my 701 to be alot tighter and has better resolution than before.
The dt880 also didn't do it for me, the 880 has a higher treble peak than the 701 to my ears, bass was similar to the 6x0 but doesn't seem to hit as deep, and vocal doesn't have 701/6x0's resolution. All three of them do sound pretty similar, but all these little difference shouldn't be overlooked.
