Sounds like a great deal for cardinals.
I did some checking after I posted and the suggestions I saw where 75-81 so 79-80 should be fine. It is at the high end for your other inhabitants I would not go any higher.
What kind of setup do you have? Is your tank planted? The fish you describe would look nice in a planted tank.
Make sure you keep up on your pwc
and have good filtration. You are well stocked right now so I would not suggest any more fish at this time. Depending on what type of filtration you have and how often you change water some would say you have 10-12 too many fish.
If ever you do thin out your tetra stock in the future rummy nose teras are fun and school well. Also, a pair Rams would do well in that size tank.