Juan, loved your tank. I also don't think your tank is over-stocked.
There are so many variables to consider when it comes to "over-stocking" a tank. I've spent years having sucessful "reef-tanks" and I'm not talking about easy to keep soft corrals either. My tanks have been SPS corrals, clams, and fish, all living in harmony. With that being said, in these tanks water quality is of the utmost importence (not to say it's not important in a freshwater tank. it is, but not nearly as critical). In some of my research in reefing, I read an artical that said the typical water flow on a reef daily is the equivalent of having a 2" fish in an olymipic size pool, and changing the water in the pool every day!
So with that being said, let's consider how much water runs "through" a school of cardinals or neons or what ever every hour. Can we really reproduce that? No! So if we really want to be a purest, then we shouldn't keep fish, or at least most fish, excluding the few that live in the wild in stagnated pools and ditches.
I'm not saying that it's ok to have 500 fish in a 55 gallon tank, common sense goes a long ways. But what I am saying is that we keep fish as a hobby because it makes us happy and that's ok, it's good. What is over-stocked to me my not be over-stocked to you and visa-versa.
We just need to enjoy the hobby we all love and stop hatin' on everyone who doesn't meet our "standards".
Make recomendations and respect each other for the place they are at in the hobby.
Abraham