In general, the e-series both increases the bass (just a bit) and increases the overall sensitivity (by 3 dB) over the corresponding i series.
As a result, I found that the SR325e (the SR325 series is the brightest of the Grado models, with the SR325i being the brightest of the SR325 series), which is darker because of its -e designation than the SR325is that came before, is indistinguishable from my SR225i (the SR225s are "middle of the road" in brightness, one of those that best represent the Grado sound, but the SR225i is going to be brighter than the SR225e, and hence ends up just like (to me) the SR325e).