Overstocking Question

[arvlyn]

I was talking to a friend today about our aquariums. We were talking about how many fish could be kept in what size tanks, etc. and Jennifer asked me if there's ever a way you "could" overstock - as in if you had extremely good filtering, kept up on the water changes, paid attention to your water parameters, etc. I told her I had no idea but would ask the experts here on the fish forums and get back to her.
Oh and we also were wondering if there's an "average" or "ideal" GPH rate for filtering.

Thanks in advance!