Nice job, The box looks very well built. Just a note on wrapping the box in carpet: you will never get it to wrap around corners nicely, you will need to cut it, and sew the corners to make a decent job. (I know this from having my sub box done) I found a guy that suppled the automotive tan matching carpet & did the labour for $70. The carpet was going to cost me almost $40. So consider having it done. The other possibilty is use tan Vinyl with a padding underneath. That, you could probably do yourself.
Don't forget to post updates!
I'm about to start mine once my stuff shows up.