I'm at the point where I do love the sound of my GS-1000's (had 'em almost a month, don't have a clue how many hours I've put on them). But it took some time for me to determine if I thought they were $600 US better than my 325i's.
For one thing, I was initially put off by the amount of bass these things can pump. But either they, my ears, or both have settled, and now the bass is just right. The bass signature is still remarkably different from the Prestige series. The SR's bass is more of a support player than a co-star with the mids and highs, more of a rumble than a punch. The GS1k's bass is a definite punch, a definite co-star. I can't honestly say I don't miss more of the rumble, but the 1k's bass is visceral enough to more than compensate for this.
So far as brightness, the 325i's do sound brighter to me, but the 1k's deliver a more true-sounding (to my ears) treble in a somewhat lower dosage. In some instances, cymbals sound so realistic to me I can almost taste the metal.
The 1k's mids are a tad recessed compared to the 325i's. Big part of that is the salad bowls. The experience vs. the 325i's is, to me, that with the 325i's, you feel like you're in the middle of it all, down on the street; with the 1k's, it's more like being somewhat above it all, resulting in more sweeping view via the increased soundstage. Big music, such as orchestral recordings, sounds that much bigger, and panning effects come across as less extreme. One can get that "down on the street" feeling with the 1k's by switching to the smaller bowls, but for me, that makes the bass a total monster (which I know many here would consider an absolute plus
).
One review of the 1k's I saw mentioned that some time ago Grado tried trotting out the salad bowls at some meet or somesuch in conjuction with the Prestige and Signature lines, but this was met with little enthusiasm. So I do wonder if the 1k's were possibly designed to sound good with the oversized pads. I actually like the oversized pads on the 325i's for some music (again, that kind needing a larger soundstage). One does lose bass response, but if you like orchestral work (where bass is usually best underplayed than overplayed) and own the 325i's, I recommend the $45 investment in the salad bowls.
So far as a sexiness factor, no way can the woodies, to my mind, out sexy the aluminum cans. Yes, the woodies do smell good, and they are light, but that gleeming, bullet-proof-looking metal -- va-va-voom!
Anyway, after some three weeks of hemming and hawing, I've decided the 1k's are worth the extra investment. But if you have a taste for the Grado sound, no way can you go wrong with either.