SA's aren't alway experts on every problem. I think going in with knowledge only makes the whole thing quicker and easier. If you can give them an idea of what you believe is wrong, that helps them and you. Your thoughts may lead them to consider something they wouldn't have previously - which they may disregard or follow-up on depending on what they know. If they know they are dealing with someone who has knowledge, they are less likely to BS you and to better explain what and why they did/do whatever service.

IMO, it's a win/win situation to go in with a knowledge base and to make sure they understand that you have a 'reasonable' perspecitve.