I'd wait and listen to the Grados with the flats. You may like them just fine. The flats press your ear closest to the driver and give you the best bass. If this is too close, and you feel the soundstage too constricted and the HF too limited, go for the doughnuts, the wonderful L-Cush ($20). These are, in my opinion, the most influential mod you can make with a Grado. They open up the soundstage without sacrificing much of the bass. They are, in my opinion, the best adaptation. If you want maximum soundstage and as much HF as you can handle, go all the way with the salad bowl cushions ($45). But be careful what you wish for, you may just get it. It's possible to go too wide and to have too much HF. Even with the famed GS-1000 (which I own), you can end up feeling like the presentation is too sibilant.
Under what conditions, then, would it make sense to own the salad bowls? When you have a rockin', warm, tubelike amp. John Grado's amp is a Melos. With an amp like that, the salad bowls make ample sense since they liberate the ear from constriction of the soundstage caused by cavernous bass. I didn't realize this until I'd purchased an M^3, which is a solid state amp that has a tube-like sound. The warmth of my M^3 turned the tables on my other Grados and, for the first time, favored the GS-1000.
But if your source is something like an iPod, those salad bowl cushions may be too much. They were for me. I found that my GS-1000 sounds better, off an iPod, when I switch to the doughnuts. Better yet, I find other Grados, like the RS-1 and even the SR-60, to be more appropriate.
If you really want to misbehave (perhaps after your warranty has expired), you could throw caution to the wind and do something like this:
I took the backs off of a pair of SR-60s. Mind you, I don't care what people think I (or my headphones) look like. I just wanted to eliminate any issues of rear-wave resonance. To pull this off, I had to superglue the headband prongs directly to the cushion, which is a doughnut.
The result? You won't believe me if I tell you. Those SR-60s had the most controlled bass I've ever heard. Everything was straight off the driver. It was such an awesome result that, even now, I'm going to do it again. I've since sold off my modded SR-60s but I've just purchased another pair, so I can create another mod. And if these sound as good as those, I'm going to sell off my GS-1000s and RS1's and SR-325i's. After all, the SR-60 has the flattest frequency performance graph. I think Grado's best idea was open-air, but if open-air is where it's at, there's no reason for air chambers. Air chambers are a holdover from closed headphones. What you hear is the driver, and when Grado started charging two grand for aluminum drivers with mahogany innards nobody can see, that was enough for me. I'm going to go with a modded SR-60 as my open-air phone (which is great when I have to hear what's going on around me, like my wife and kids).
