Just saw this..
CNT can be hit or miss. I wanted the cat out of the engine bay and a nicer looking piece so I went Cobb, only other option I'm aware of that puts the cat out of the engine bay is the Turboxs.
A dw65c helps and is easy to install. Is it necessary at this level no. I have seen a few oem ones that were on their way out.
BPV, I recommend it at stage 2. As I've seen low mileage 08+ WRX leak (same as ours) at stage1 levels. Will you feel it while driving? Maybe depends how bad. If you check CT08's build thread you can see where his is bleeding off boost.
The grimmspeed EBCS works great and helps shape the boost curve. Again not needed but a nice add on.