I used poplar in my home, it is cheap compared to other off the shelf materials. It took stain very well, but a word of caution, the heartwood of poplar is green, takes stain well, and when it ages it turns a nice shade of brown from UV exposure. The sapwood is the bad guy here, it is really light in color, as soaks up the stain, so much so, that if there are any dark pigments that make up the stain color, for some reason the sapwood really accentuates the dark color, when on the green heartwood it responds differently to the color of stain being applied, so much it looks like 2 different stains are being used. This problem was not evident when I built my home in 1989, poplar then was pretty much all heartwood. My remodel that I finished last year proved different using poplar. Poplar today has a lot more sapwood, and just a little heartwood which makes it difficult to stain evenly. Maple has the same problem but for a different reason, but the fix is the same. There are "wood conditioners" out there that are applied first to soak up into the softwoods or "curly grain" like maple that will let the stain soak in evenly, at least more evenly than without the conditioner. This may be the simplest fix for the problem, though there are other ways to get past the problems, but they include a lot of trial and error- time consuming.