A pair of dwarf
Gouramis can be kept starting at 15g min. Need pH range from 6-7.5 and hardness 5-12
Angels should be kept in nothing less then a 50g and need need pH 5-6.5 and hardness 0-5
With the knife I assume you mean livebearer that can also be kept starting at 15g and ph 6-8 hardness 5-20
That said, I'd def not recommend the Angels in such a small tank, apart from their requirments they grow to be 10-12" incl the fin's and would have a hard time to manuver around in your tank period.
For the basement vs tank: I don't think you'd have to worry about cooling since it doubt it'll exceed 80's in the summer period. Heat however will be a concern considering you wanna house tropical fish hat got to be kept in the 80's. Therefore I suggest a heater far larger then your tank size standard recommendation, something around the range of 250-300w min, here's the heater's I started using and love them as they allow you do dial to a certain temp and are fair enough in price really Cascade Heaters, Heaters | Pet Solutions
I'd strongly suggest getting a Liquid test kit set (for example by API), it will not only help you to determine your water parameters now to help stocking the tank, but will allow you to monitor them while your tank is cycling (which usually results in different readings) and also its the easiest way to follow the cycle really to tst ammonia, NO2 & NO3
Do you plan on planting the tank as well?