Asr got it right. Don't waste 200 $ on an amp. I have an RS-2 (and also had RS-1). These cans don't improve with better amps (and certainly not with cheap ones). I have tried Musical Fidelity X-Can V8, my Earmax silver and the head-out of my pre-amp. The Earmax makes Sennheisers fly, but the Grado sounds the same out of all three amps. Exactly like it sounds out of an iPod (with excellently ripped music of course).
Indeed, I'd say put your money preferably into the RS-2 instead of a cheap amp. A good Dac would be key, as Asr pointed out. A V-Dac from Musical Fidelity is a good one around 200 $, but then you also need an amp to control the volume. An ok amp WITH Dac would be the X-Can. It can also serve as pre-amp and may be around 200 $ used. Another excellent Dac/Amp combination is the Lehman Black Cube linear, certainly north of your budget.
I think a good way to get good sound out of an RS-2 is simply an iPod.
While I write this, I listen to a Bruckner Symphony out of my many years old iPod shuffle (the white one with 1 GB) using the RS-2. I have bought one of the best recordings that is available (now, THIS is key) and ripped it with a high accuracy tool. Couldn't sound any better, not even from the Earmax..
Edited by mironathetin - 10/31/11 at 12:48pm