Hello SamHarris,
I think the changa your talking about might not have enough harmalas in it, sure the effect will be different from smoking only dmt-crystals, but I think smoking caapi leaves before would be a better option if you want to potentiate your changa.
Smoking plain caapi leaves gives a little change to the experience, but I personnaly prefer smoking 10X caapi leaves before smoking changa ( or X5 / X7 ), the difference is nothing near to "little change".
But this is my opinion, and to be more confortable with your changa, you should try it the way it is, then ( of course after coming back to baseline again ) , retry after having smoked caapi plain leaves ( a bowl or two ). You will see by yourself the difference.
And if you want to go deeper, 10X is the way. (It is really easy to make it, a quick search on the nexus will lead you to the process)
You can also try the 10X caapi by itself, if the original leaves are potent enough, you could feel something, some people do, other don't
Have a good journey.