Which Grado equals the HD600?

The Grado house sound kind of screws with direct comparisons, but the SR 325is, RS 2, and PS 500 all are similar in detail retrieval to the Sennheiser HD6xx. Grado just portrays it all differently.

When it comes to just detail..

SR-80 = HD-600

SR-225 = HD-598

SR-325 = Q701

...runs away

Please don't give me this treble excuse

I think HD-600 was meant to be fairly forgiving. Even more so than the 598. Yes, I said it. Sorry.

To me, just because a headphone is more expensive doesn't really mean it's more detailed. I have $90 headphones that have more detail than the HD-650..doesn't mean the HD-650 isn't good.

I feel/felt that the SR-225 was about on-par with my HD 580, but I didn't feel that the GS-1000 did $800 of improvement over the SR-225. The SR-325 rang more, and was less comfortable; wasn't impressed. I'd skip it and get the RS-2 if you want to spend more (I've never heard the RS-2, but I really disliked the SR-325, and hope/assume that the RS-2 more appropriately fits somewhere between the SR-225 and GS-1000).

I agree that the HD 580/6x are not the most perfect headphones in the world for detail retrieval; there are many headphones I would rank "above" them in that respect. I have not heard the 598 though. I think the 580 and 600 are better than the 595 though (and to be quite honest, better than the SR-225 for overall usage). 

The K701 is a different beast; it bests the Sennheisers in detail retrieval and is a more analytical headphone. I don't think there are any good Grado analogs. The GS-1000s perhaps, but you're really talking different planets here. If you want something that can equal or better the K701 in detail retrieval, speed, etc; I would look at Sony (specifically the MDR-F1 and MDR-SA5000; and if reviews are to be believed, the MDR-CD900ST). I think the SR-225 is still a great headphone for the price, but the differences in headstage are just so dramatic when you start talking about the K701, that it makes any comparison hard.