Looking for advice on exhaust

[pdelosa]

I'm new to diesels and looking for some advice for my truck. I have a 7.3. My goal is to improve my fuel efficiency. I've already installed a K&N intake on it and plan to upgrade the exhaust next and eventually and ECM tuner. What I would like to know is what exhaust should I go with? I'd like to stay under $500 and I don't want to be excessively loud. I know that the truck is going to get louder when I change the exhaust I just mean that being louder is not my goal. I have found a number of exhaust kits in my price range from summit, aFe, and magna flow. I don't know any thing about any of these companies and who makes quality products so any input would be appreciated. Who are the best manufacturers of diesel exhausts?