I've got the SR225's, the RS-1's and the HD650's. I've also tried the SR125's, SR325i's and HD600's over the last 6 months.
What I've learned from all this experimentation is:
1. It's the total synergy of the source, amp, phones, headphone cables, interconnects, and power cords... and oh yes the ear pads believe it or not, that make the sound - good, or bad. The sound will not be much better than the weakest link in this chain. So, for my money, I wouldn't invest too much in any set of headphones, if any of the rest of this chain is not "top notch."
2. The SR225's are the greatest value in the Grado line, including compared to the RS-1's and RS-2's. They're often referred to as "the poor man's RS-1" - and it's absolutely true! "All other things equal," they sound virtually identical to the RS-1's - just 5% less bass extension, and 5% smaller soundstage - everything else is the same. The SR125's are too sibilant and the bass is a bit weak, the SR325i's are too sibilant, and the bass and lower mids are a bit too strong. The SR225's are "just right," although the highs are still a bit bright. But, the bass can be improved and the highs tamed by simply reversing the bowl pads as suggested earlier in this thread - reverse the pads and they are truly outstanding! Forget about the overpiced Flat Pads, I've tried them and returned them - they muffle the sound, eliminate the highs, and muddy the bass. And... if you read most of the reviews and comments of the SR225's that you can find at Headfi, or Audioreview/Audioholics, you'll find they agree. The RS-1's are great, also, but not for their $400+ premium - and, as I said, they're only 5% better.
3. The HD650's may well eclipse all of the Grado's... with the proper source, amp, cabling, etc.... and... if they're "de-veiled" (a trick I learned elsewhere on Headfi). I removed the stock foam lining in each phone (which is all you need to do to hear the dramatic improvement), and replaced it with fiberglass window screen mesh from Lowes / Home Depot, just to protect the drivers a little more. The foggy veil was eliminated, and the sound became instantly much more dynamic, crisp, and clear - much like the Grados, but with a much bigger soundstage, and bigger bass (although still punchy, tight and well defined). Of course, this is with the Cardas Cable, and 100+ hours of "burn in." I understand from others on Headfi they also sound great with the much more expensive Zu Mobus cable (same dynamics and clear extended highs). But, they don't really clear up without the "burn in."
And if you really want to get the best out of them (truly phenomenal, world-class sound), you can mate them with the Musical Fidelity XCAN v3, X-PSU v3 (power supply), with the Revelation Passage Cryo-Silver Reference Power Cables, with the Music Hall MMF CD25 1+ CD player. This combo produces the great warm, lush, liquid sound of tubes, combined with the tight, punch and dynamics of solid state. I understand from Headfi, they also sound phenomenal with the Lehmann Black Cube Linear, as well as the Gilmore, and Ray Samuels amps. But without the rest of the links in the chain, you're best to stick with the SR225's!
Believe it... or spend your money and find out.
650smile: