The W11Rs are impressive cans, I do have to say. I chimed in because I do have a set of m50s, bought them before the craze on here about them. I was not acutely ware of the rest of AT's lineup, esp. the esoteric boutique models like your W11Rs. Again, very impressive. If it works then it's pretty damn cool because this is my experience, maybe not in the same dollar bracket, but I have some experience with this. I am going to reference some of the budget hacks and tweaks experience I have had in grado/headphone modding, and since I love my sr325is, I am certainly a fan of Grado's sound.
I have been modding stuff left and right out of all the spare parts I have piled up over the years, and so I think I have some basic ideas. I know it's an old thread, but I have been just playing with modding another set of cans and in doing so I came across this set of experiences.
The Denon D1000s, the "budget" denons, the ones that the Aurvana Lives! are about 99% sharing the same parts (including driver and baffle), gives these a mini-d2000 mod, but with less dampening inside the shells, and you will have an extremely open sounding 'phone that can hold up with the lower Grados.
The problem for you is the lower Grados difference between the sr325is, lets say for example, is really not that much. You would have to really tweak a closed set of cans to get that grado sound, and you still would not have that signature "speed", as that is very hard to find in other headphones, and is a reason there is love/hate for grados to begin with.
Your best bet is to mod up your Grados, as you can get some amazing improvements for less than it would cost to mod a decent closed can to have that speedy open sound.
Beyer DT990s, but modded as a "closed" can, might get you close, since the DT990s are somewhat grado-ish in their speed and soundstaging, but still it's a totally different world once you really get into it. Look it up, though, there is a Beyer expert here that has done more beyer mods than I have ever done, and one was to experiment with various ways of taking the DT990 and "closing it up". If you get *most* of the 990's signature in a closed can, you are getting something like a grado, not sure what model, but there will be similarities.
I recently been playing with these cheap Radio Shack "titanium" headphones, and while they are open, they sound very much like an SR60, so much so that I took the drivers out and put them in my *old* sr325 barrels, and my eyes went What as the drivers fit perfectly. I mean it was like they were designed to grado spec. Strange. They sound good too, probably better than in the plastic radioshack headset... better than stock sr60s, but then, it is hard to measure since the driver is what makes a grado a grado, IMO. This is going from open to more open. Not exactly what you want. The drivers, I am almost 100% are koss drivers, the ones used in the 25th anniversary ed. PortaPros. Why they seem to fit grado barrels so well, who knows? Koss is always raising eyebrows.
An alternative would be to give the Sony XB700s a shot. The XB1000s are out, but I don't think they are near grado territory, however, the signature grado mids and staging, it's all there and more in the XB700. I would not discount this 'phone.
The d2000 is too slow.
The AKG271s (S as in still made in austria), closed back studio monitors that can sound extremely grado-ish... I have to EQ them somtimes because of this, as I don't want a monitor to sound like an sr80, but they are closed back, and might do the job better than previous suggestions when I think about it. There are new versions of the akg27x, but the original 271S is the way to go.
The AKG301xtra is a strange semi-open phone that plays like a closed can that sounds like an SR60, but costs way more. It is blue, and not sure what AKG was thinking, but I got them as a gift from someone getting out of headphone hobby. They have smaller verimotion drivers than the usual AKG models, so you have to have some heft in your amp, so no ipod or any portable on these guys, but out of a preamp headphone port or dedicated headphone amp, they sound almost exactly like SR60s. It is uncanny. I don't recommend them because it is a lot of BS to go through to get a headphone that sounds like a really good can you already have that can be modded to sound *maybe* as good as the SR125is. You could take them further and get close to the 225s, as there are folks on here that have done such a thing for not that much money. Replace plasic grille with metal, and get the bowls for pads, and some other minor tweaks gets you darn close. It is hard to justify the sr125, but the sr60 can be taken far, the sr80 even farther, but obviously you would not get a set of 325is without the metal barrels.
There is a link somewhere on here about sr60 mods, but you can use whatever low end grado/allassandro to take them to something in between the RS2/1 and the sr325is. You just need to be able to work a router and some PVC pipe for the larger air chambers of the larger grados. I have not done this, but I have no doubt it would sound damn good.
I am not sure you are going to get as much performance for your dollar trying to get a grado signature sound in a closed headphone, but yeah, like I just talked about, you can come close if you have some beyer parts about or feel adventurous and want to try some AKG271Ss. I doubt they would match the W11Rs however. Those ATs look NICE.