Heya,
Grado pads are hands down the biggest and fastest way to change a Grado headphone. I've bought the SR60i and SR325i to test the first and last of the particular prestige line to see if it's worth it. Basically to see if the 325i is actually worth another $220 or not. I bought all the pad types too, to test them as well on both headphones. I have to say, after spending time with both headphones, the SR60i and 325i just do not sound that different. Both sounded great. But I definitely did not get an impression that the SR325i was worth the price tag difference, as it was just so similar. I guess that's more testament to the value of the SR60i than anything. However, what did make a huge difference was the cups. SR60's come with those flat discs. They were awful. When I first heard my first Grado, it was on those flat discs that come with it and the sound was pure treble, it was awful I couldn't believe they shipped like that. I quickly put on the L-cush pads, and man, what a difference. Good balanced sound now. Excellent bass response by comparison, tamed treble, and solid mids. Then I put on the G cush pads to go bowl, which are large enough to be over ear, so much more comfortable. But the sound? Oh man it went south, the sound was like pure treble again, the treble soared to new heights of hot and tizzy, it was quite fatiguing, the mids were still there, but the bass pretty much went away again and it was like having treble domes on the ears. I did the test with the SR325i as well and had the same results. The L-cush pads sound wonderful and I consider them mandatory for any Grado that doesn't already have them. Comfort is not ideal. But the sound is ideal to me there. It's the only pad that I felt the bass was appropriate and not overly taxing on treble and mids. The G cush pads are super comfortable, as they raise it to over ear, they're huge. But the sound is not good, it's hot treble, and you lose some bass, so it just doesn't sound right. I think the G cush pads should be reserved for a Grado that was built around using G cush pads from the ground up, which the prestige line is not. Verdict: Get the L cush pads, they're an excellent improvement if you don't already have them. Avoid the G cush pads for prestige line.
Here's the flat discs the SR60i's come with (awful, unbelievable, every Grado should come with L-cush standard):
And again, I found the SR60i with Lcush to be basically as good as the SR325i. I didn't hear a $220 difference. $20 ear pads made more difference to the sound, by far.
Very best,
My memory could be faulty. (ya think?) It's interesting that one person can hear big diffs and another person can hear small diffs on the same comparisons. But, basically, I'm a leveler, not a sharpener. I listen to a lot of classical and prefer the orchestra spread out more rather than squeezed together. 
