I started with the SR80, loved it, but got greedy and upped to the SR325i. When I first pulled my 325s from the box, I thought the 80s sounded better. It took weeks of ordinary use for "burn in" to do its thing. Months later, I came into some cash and upped again, this time to the RS1. This time the shoe was on the other foot and it was the RS1 that had trouble keeping up with the 325. A few months later, luck came my way again and I upped to what was then the king of the mountain - the GS1000. You can guess what happened there. Until I could fully burn in the GS1000, I swapped out the jumbo pads for bowls, which sliced away the sibilance and left me with some major thumpers.
I've since sold off all those cans in favor of the top and bottom. I have a pair of PS1000s and a pair of SR60i's. I also have a pair of woodied 225s I'm modifying further. Having owned two pairs of iGrados (which are cheap and sporty but which lack much in terms of air chambers), I've owned all the non-exotics except for the SR125 and the RS2. I've also owned two pairs of HF2s (great value for the price).
Believe me when I tell you that an SR60 or SR80 could serve you well right off an iPod. I wouldn't bother with the iGrado because it's not only the lowest entry in the product line but the SR60 is just so much better. There's only a $20 difference between the SR60 and SR80. If you want peace of mind, buy the SR80 for whatever benefit it offers. The classic SR80 differed from the SR60 in one respect: It had bowls instead of comfies. With the current "i" line, both come in comfies and I'm hard-pressed to tell the difference between these two - except that the 80i is supposed to have more HF - which can be better or worse depending on whether you're looking for a mellower or sharper presentation.
Some say the SR125 is the best deal in the lineup (I've never heard it so I have no opinion) while others rave about the 225, which I've heard and have and like very much. If your budget is $120, there are a couple of choices you could look at. You've got the $79 SR60i and the $99 SR80i. The differences between these are not worth losing much sleep over. If you want more thump, the "flats" sold exclusively by TTVJ (that rat b@#$#rd who cut my throat when I tried to resell my last HF2 - price cutter!!!!) provide it in spades. $79 + $35 = $114 + shipping. That's a great combo, which you can tweak (if the flats go too far) but gently cutting the center hole slightly wider (just don't go nuts with your scissors).
As I've mentioned elsewhere, I bought a pair of SR60i's, punched out the driver vents (all 10 of them), swapped out the comfies, replacing them with jumbos (Hello, HF) and used felt to damp the inside. Recently, I pulled out some of the felt lining the inner chamber walls and replaced it with thin, bendable, strips of wood. The result was surprisingly effective (I didn't know if that little wood, mixed with plastic, would make any difference but it did).
If you buy cheap - SR60 or SR80 - you can afford to enjoy the Grado house sound and mod or tweak it up as time and opportunity permits. But that's what appeals to me. You may just want the package so you don't have to worry about it. One more option to consider is the MS1, which is sold by Alessandro. It uses the same Grado drivers and architecture but tweaks it. Those who've bought these have come back very impressed. In fact, the MS1 ($99) is considered the equivalent of the SR125 ($150), so you've got a bargain there.
When I need a knockaround, I put my money into SR60s and fix them up. That way, if I lose the headphone (or someone snatches it), I'm not out much - and the sound (when tweaked) is terrific.
