I think there's a person on Ebay who makes adapters that mount onto existing plastic Grado cups and allow you to utilize the grey velour pads from Beyerdynamic. Being that HifiMan has released the offering of their Focus pads, I think it would be interesting to see how they might be able to integrate into the Senn Grado configuration. As I mentioned, I didn't feel that any bass was really lost at all. The setup the guy sells on Ebay runs about $90 with the Beyerdynamic pads.
I'm now curious how the Focus pads would work with a StratoKosster closed headphone configuration. That's the general direction my compass is pointing, just not sure exactly where I'll land.