john:

You didn't say you had a trademan who has done similar work which you already admired; that changes things entirely. No offense meant, but in your post you sounded like a novice to woodwork so my advice on using "store-bought" cabinetry was based on that level of experience.
If you've got expert help custom is always better.

I decided on 3/4" Oak plywood with solid Oak shelving and face framing for appearance sake only. Since the cabinet is built in the wall and has doors I somewhat discounted the direct effects of resonance on my shelving and cabinet sides.