I doubt the front is poplar, but I am not a super expert.
It's probably birch or maple.. I think Alder is more of a West Coast wood, but maybe the cabinets were manufactured out west? I have never used Alder, but it seems less likely than birch or maple.
I would use birch or maple. Birch is going to be less expensive. Maple plywood is pretty expensive. Even if you knew that the front was maple, the color will vary slightly from from the different species of maple (and even different trees in the same species).. I have two piles of maple hardwood in my garage. One is almost a white color, the other is a light tan..
I guess what I'm saying is that part of the charm in working with wood is that everything is not necessarily totally uniform in color, like mass produced furniture is.
So, if it was me, I'd probably use birch plywood.. 99% (or more) of the people can not tell the difference.