Yes, I think you will be covered
It is wise to have another outlet for your sub, separate than your equipment. While I think you can get by with less, if you have the room in your breaker box for the extra circuits- you will never regret having more than you need.
I think you will be fine with the 15A. The only place I might want a 20A for future use is for the front outlets for your main equipment. But you've got the 2nd circuit on the sidewall too. If the walls are still open you could run #12 wire and replace the breaker with a 20A, but probably not necessary.
good luck with the project- have fun
