I actually have the original model (so neither i nor e)! Whatever differences exist between the three iterations are (so I've heard) not terribly substantial. As for the frequency response, I would say that the SR325s are somewhat brighter than the SR60s with more sparkle in the high-end and more presence in the upper mid-range. Looking at the frequency graphs from Innerfidelity seems to corroborate my personal impression.
https://www.innerfidelity.com/images/GradoSR325.pdf
https://www.innerfidelity.com/images/GradoSR325.pdf
The only meaningful comparison with regards to detail would be a pair of HD650s that I've heard a few times (though not at any length so take this all with a grain of salt). The level of detail is certainly comparable to my ear, although the HD650s were a touch clearer and more precise. If I were to make a direct comparison between the two with regards to detail, I would have to give it to the Sennhesiers. That being said, the HD650s are a good deal more expensive and substantially much more difficult to power. Further, I would say that the Grado sound signature is much more enjoyable that the extremely flat reference signature of the Sennhesier HD series.