There's a lot of us around here...
As far as woods go it's really all up to you. I've heard a few different ones and didn't prefer one over the other. It's more about the way it's shaped and the material used to secure the drivers. There are quite a few well known names in the custom cups game. Lawton being the biggest one.
Just pick the one you think looks the best honestly. At least I didn't hear a difference.
The E9 does not have a DAC. The E7 is the only way to get a DAC from the pair.
EDIT: To clarify the E9 is only an amp.
I mainly listen to my avatar/alternative rock and classical music. Trying both out is a good idea. I'm mainly looking at the 650's and the Rs1i.
Both the E7 and E9 have DAC. You can dock the E7 in the E9, but I don't fully understand the benefit of having both of them.
Many thanks for your help!