In an ideal world, the res will be the highest point in your loop. It makes bleeding air out of your loop extremely easy. In the real world, this isn't always possible. As afzsom said, once you're bled out, it's all the same. The position of one component in relation to any other is irrelevant. If you need to turn your case on its side to bleed easily, then do that. Don't make decisions on how your loop is going to be oriented just to facilitate something that will hopefully only happen once or twice...