If these are the normal bias Lambdas, which seems to be the case, you also really should consider damping the drivers. There is some very open foam you removed, and since you mentioned removing the dust covers, you almost certainly also took out the damping pad. I really did not enjoy my SR-Lambda undamped, but love it with the stock (or approximately) damping material. I guess it is even worse for you, as that dust cover should be providing some additional damping.
On another note, I got my first really good listen to my new Lambda Sigs. I have to say, I am not hearing the love. Damn things are too bright for me, in such a way that I would probably put them last right now of all of my electrostatics. Bass is also disappointing.