That looks nice and sturdy. I saw you are planning on putting doors on it, i did that one mine and it cuts the noice down quite a bit.
I made an enclosure for my cnc as well. I got the idea from ECRC's enclosure.
It's made out of 3/4" mdf, the back is made out of hardboard and the windows are plexi. There is a replaceble furnace filter filtering the air to the computer/controllers (behind the monitor).
When the picture was taken i didnt have the door in front of the pc on there but its on now Picture