I make mine just exactly as you do and I have found that the quality and even the nature of the broth is really really important too. I have a bag in the freezer where I throw stuff to make a vegetable broth every week or so. I find that when that bag (which always has a lot of celery and onion bits in it, carrot bits, a smashed tomato or two is the usual thing) has a really high ration of mushroom stems that the resulting broth is perfect for the quinoa.