This is one of those questions that have a variety of answers and and tons of variables. Also, you can have two identical set-ups, identical water, filtration, etc. and I guarantee you there will be two different results. I think most if not all people strive to find that balance you seek, but seldom find it long term because your not dealing with controllable factors. If your looking for advice on your set up, I have a 125 and your welcome to come by and take a look. One thing I noticed in your post is the water changes. I used to do 5-10 GAL a week and my tank started having filtration issues. I found that for me 20-25 GAL a week has been much more affective and my tank is much happier.