Yes and no.
If the related text you choose to refer to links in with the main idea you are trying to articulate, particularly in relation to the techniques you highlight, it will raise the quality of your response.
However, if you choose a text, which, whilst relevant, doesn't emphasise your point you are making, or drags away from it (or just isn't answering the question) - you can say good bye to a band 6 mark.
Be very meticulous in the quotes/techniques you use in your essay. If the related material's quotes don't provide insights into your point - ditch it all together and find a better text that does this.
Good luck