Looks like a good plan so far.
You might also wish to consider acoustic panels on the walls. Given that you're starting from scratch, you might be able to use something instead of what you're already planning for the walls. I met a chap a couple of years ago who'd done it himself. Not sure what he used, but it clearly worked well, and once painted, looked just like a normal wall.
If the amp you are planning to use doesn't have room correction, that's also worth considering, as it can be extremely useful in the right place.
As a final point, you're planned audio rack is looking a bit light on space. Given that you'll be starting with an amp and BD player, potentially then adding additional power amps and other sources, might be worth over-specifying it. As it's a new build, also worth considering given the audio components a dedicated electrical ring, to reduce noise from other electrical items nearby.