Nice tank, but 50 fish is way too much for a tank that size, even when most of them are small.
While the fish might be still alive after a year, it doesn't mean they could be doing much better. Filtering is not the main issue, because you seem to think that a bigger filter give you more room to add more fish. The main issue is stress, something that you often only see the negative effects of in the long run. It's like stress with people; on the outside you might not see anything wrong, in the long time several physical problems might start to pop up. You see the same problem with birds and other animals.
Getting that bigger tank is going to have a positive effect, but if you start adding lots of larger fish, then you will continue to have this problem of overstocking.
Anyway, it's your tank, I'm just giving you some well meant advice.