I am hesitant to give a measure of inches of fish/gal or per surface area, because that gets so contentious. I tend to go for about 1 inch/gallon. Regardless of the way you measure it, you can get away with more smaller fish, because they have higher length/volume ratio than bigger fish, which means there's less metabolically active tissue per unit length. An 8" oscar needs more O2 and makes more ammonia than eight 1" tetras.
The factors I consider limiting are
1. Water quality. This is the most commonly cited reason. More fishmeat in the tank makes more waste. Most tanks nitrify well, getting rid of the most toxic NH3 and NO2. However, nitrate will stress some fish, and messes up your tank's buffering system, making it more acidic. Oxygen is less of a problem in a well-filtered tank with lots of turnover, but see "safety factor," below.
2. Behavior/aesthetics. You want fish in numbers and combinations that will make *them* happy. In many cases this means fewer fish than the tank will hold. Very dependent on the species.
3. Safety factor. If you are pushing the envelope, then what will happen when a snail gets in the impeller of your filter, power goes out, or whatnot? I had a 100 gal, filled with Haplochromis that I had raised from babies, which was truly spectacular until I was away and the filter failed. Heartbreak. You can't expect things to live indefinitely without filtration and heat, but keeping stocking low is good insurance.
By the way, what kind of fish are they? It sounds like you have heard plenty of opinions about your stocking already, but I am just curious about what you have. If they are perky and colorful, that's great.
ed.
After thinking about it, boy, that sounds like an awful lot of fish. I'd keep a close eye on them.