Mikec ....I haven't heard the RS-2s, but the genreal consensus on the headroom.com discussion forms is that RS-1s(which I have and love) are much better. You may also like the Sen 600's too.
I agree, out of the box, the Grados are VERY UNcomfortable, (itchy as hell): Grado defends the material as sonically superior, but I think they ned to listen to their customers instead of just their headphones!
I found that my RS-1s were almost unbearable until I took the leather earpad covers off a pair a pair of 20 year old Stax electrostatics and fitted them onto the Grados -- the covers fit perfectly and the Grados now easily pass the comfort test -- I forget they are on at times. If you try a simalar tweak, make sure the inner portion of the earcup is not covered -- just the part that touches your ear, otherwise you may muffle/interfere with the sound. Also, search headroom.com as I think their are few threads on improving the comfort of the Grados.
I suspect some of your problem may be you Classe SS 50 -- a home theatre processor that may be a touch too forward for truly revealing headphones. I'm not knocking the Classe -- even my First Sound Refernce sounds bad with the RA-1 as most preamps, even those of reference quailty, are not designed with headphones in mind. (Sonic Frontiers and Melos being the exception, as SF licenses the headroom stuff and Melos has a well reviewed headphone jack).
To give you a very close analysis/comparison soon, I have have a Classe 60 Preamp and I will be testing the RA-1 through the Classe in a couple of weeks when I do the "head to head" (no pun intended) between the Sens 600 and the RS-1.
If the Classe is not to blame, then it's probably your source or source material.
A good test for the RA-1 would be to couple it to a decent analogue setup, failing that, a GOOD CD or CD/DAC. (I use a Sony SCD-1.) I would suggest you take your little RA-1 into a dealer with a EMC-1 CD player, Meridain 508.24 or other well reviewed player, or top notch DAC such as the Elgar/Purcell, Levinson 360s, etc.
What's more, my RA-1 sounds bad with poorly recorded stuff (that's the problem with reference quality gear -- it brings out the good AND the bad) For example, even on SACD setting, the Sony SACD remaster of "Boston" still sounds far inferior to the old $6 vinyl that I used to listen to for hours on end 20 years ago.
In sum, I think your RA-1 is NOT the weak link you think it is, since mine sounds so very good when hooked directly to a Class A reference source (SCD-1) playing a well recorded SACD.
So, my advise is to cart your ear can setup into a dealer with a SCD-1 or Marantz SACD player and plug it directly into the SACD player's output. If you still don't like the sound (and you will) then, and only then, start looking for another headphone amp. But be prepared to spend over $800 to beat the sound of the RA-1, as you'll need to look at the top of the line Headroom amps (Headroom Max) or the Wheatfield tube.
Hopefully, I'll have the Sen 600's here in the next two weeks and thus I will be able to start my review that may answer many of your questions. In the mean time, get yourself a copy of the latest Sterophile, where they review a $6K Stax earcan setup with both SS and tube headphone amp. When I read between the lines of this review (which I find is essential for anything Sterophile writes), I noticed that the reviewer still thought his Sen 600's were close, and he was not completely sold on the Stax sound -- especailly not at $6K. --Lorne