Design/construction question

I've posted a sketch of a fireplace surround in abpw. I have a question
regarding the upper doors.

Given that they're each 53" by 21" (20" for the doors on the right side),
what wood should I use to ensure enough strength and stability. These doors
will be muntined with 8 lites each. I'm thinking that the lites will
actually help prevent racking if they're properly fit. I was planning on
using 7/8" thick by 2" wide for all rails and stiles.

This entire unit will be painted so appearance of the wood isn't an issue.
Still want to avoid the large pore structures, though (ie, ash, oak, etc...)

Do you think poplar would be strong/stable enough? Any other
design/construction input?

Opinions appreciated,

JoeC