I don't know what you guys are all talking about. The SR325is are absolutely incredible headphones. I believe that the main gripe most people might have about them is that they take no prisoners and will reveil ANY deficiencies in the source, sometimes brutally. They simply reproduce the information that's fed to them, so don't look at these headphones as a weak link, look further up your audio path.
From what I can gather, the SR325i was the gold 50th anniversary edition, but other than that, they are basically the same headphone - except for a few VERY minor tweaks (and I do mean MINOR tweaks) here and there. In respect to those tweaks, however, unless you have absolutely top class equipment, you may only be imagining that you are hearing a difference. These are the only headphones (and I've owned many) that enable you to hear right through the music - they are just so detailed and in fact probably too analytical for some ears.
If you want a warmer sounding headphone then I suggest the RS1i or RS2i - they are just as detailed as the SR325is, but because they tend to sound a little on the warm side (probably to do with the mohogany enclosure more than anything else), they also don't tend to be as fussy about their source.
So, to "White Noise", don't be too concerned that you have the "i" versions and not the "is" versions. If you are not totally happy with them, save a bit and improve your source. Enjoy!!!