I used a minwax gel stain on my cab. I get a lot of compliments on it, it leaves a great patina, makes it look kinda like its antiqued.
It won't bend unless you expose it to cycles of heat and moisture. and the structure itself will keep it from warping. Just make sure that the sheets you buy are straight. Look them over carefully, lay them on the concrete floor and see if they are flat.
23/32 is basically 3/4 an inch. You want 3/4 an inch plywood, you can probably get by with 1/2 inch also, strength won't be much of an issue, all you need to do is hold up a TV, and you can reinforce that area and build an inner frame of 1x2's
Last thing though. I am not sure if staining is the way you want to go for the type of cab you want. A large 4 player CRT cab will be pretty big and if the stain doesn't match the rest of your furniture it will stick out like a sore thumb.
Personally, I think stained cabs look best with a slim/lcd build and a simple CP. THe CRT cabs I have seen that are stained just don't look as good to me, if I were building what you are building, I would probably paint it. It would give you more lee-way with the build. But that is just my opinion.