If you are squatting heavy, as you should be doing if you are training with the goal to increase your overall strength, walking up a couple floors shouldn't be too hard of a task and I am pretty sure there are more benefits to it than it would hurt your other goals.
I can attest to the fact that stairs are a breeze to climb if you're squatting heavy, and I'm not even squatting that heavy.
Stairs are a breeze to climb if you are even moderately fit. (Even climbing stairs will make you fit enough to climb stairs.)
Just climb them faster (=more power), and make it HIIT.
What if you going up say 3 stairs at once with every step? Fair bit of power required from the legs.