It sounds like you've made your decision so there's probably no harm in throwing you a comment from out in left field, which is where I spend a fair amount of my time.
I don't think there's much difference between the SR60 and the SR80. Classically, one came with comfies while the other came with pads. Not surprisingly, it was the SR60 which had the better bass while the SR80 was more open. Now that both come sporting comfies, that tonal difference comes down to some tweak of the driver, with the 80s having the slightly brighter presentation. If it's the kind of decision that will haunt you, spend the extra $20 and forget about it. Or by the MS1, which has the same feature set as the SR125, though its fans obviously think it sounds better.
If it were me, I'd buy the SR60 and take that $20 and use it toward a cable upgrade - not a commercial cable but a four-wire braid of 24 AWG 99.99% silver. Get at least two colors the same so you can run separate ground wires, then solder one end to your Grados and the other end to a gold-plated connector ($4 at Radio Shack). Four feet of wire (enough for an iPod) will cost you just under $50 plus shipping. After laughing at the cable freaks, I was surprised at how much better things sounded in silver. I tip my hat to the silver wire, though I still laugh at those jerked-up prices for commercial cables.
If you want more bass, open up the shells and vent 1 to 10 of the little holes that surround the driver back. The holes are covered with a thin paper/cloth designed to allow in a certain amount of "bass reflex." The big Grados have between 2 and 4 of these holes popped. I went whole hog and popped all 10 on mine. As a result, I don't have any problems with bass. I get so much bass, I'm often tempted to switch to the jumbo pads on my PS1000. I just don't like the clumsiness of those big jumbo pads (plus my ears get hot and sweaty inside those big muffs).
You can also damp the interior chamber using Dynamat. I use adhesive felt. Either way, it cuts down on the HF spikes. For less than the price of an SR125, you can have an SR60 that beats everything short of an SR325. But that's if you want to get your hands dirty. The nice thing about just making a choice and running with it is that you get your feet wet. Only after you've gotten some experience with these cans will you really know what you want. If upgraditis hits you, sell what you have and put the money toward your next object of desire.