Yes, that answers it, sort of. The problem is HP and its competitors don't document upgrade options properly.
I spent 10 minutes trying to find out how much room you have for a graphics card in there. I think it's up to 10" and double-wide cards are OK.
If true, this means the Sapphire 270x would fit.
Take a look inside the case. Get a ruler and see how much room you have from the end of the existing card to the hard disk cage on the other end. If it's 10" or so it's good. Also, see if a card that takes two slots would fit. The card you have in there now is single-slot.