I love Severums, they are the absolute best fish
I had a 8 inch female before and she ate out of my hand!! They are very trusting fish , and they are also beautiful. Greens are nice but, personally i like the turquoise better. Aspurguru: that is a big rip off, usually a large one goes for about 30$ but, we barely ever see green around here , so i don't know if it is more $$$ for greens. IMO you should really get rid of the silver dollar and replace it with the severum. Oh and you will probably need a larger tank for the oscar later.
Pacus really shouldn't be kept as an aquarium fish unless u have a 250 gal or more. Anyway good luck