Then effectively you and I are in the same boat. My advice would be to try both and decide which shoes deserve L vs. XL, in the same way that I use both S and M. So if you can't mix and match, I would suggest you get 3 S and 3 M for $50 plus tax and shipping.
As for width, you can just think of it as a tiny bit bigger. So picture an 11E as effectively an 11.1 or somesuch; bigger than 11D, but not as big as 11.5D.
Now if we start talking about EEE or AAA, I really couldn't tell you for sure.