Severum, geophagus, acara stocking question

[Ma Bell]

I am redoing my 125. Id like to have severum, geophagus sveni, and possibly electric blue acara. How many of each is ideal without overstocking? Do they need growout tanks before the 125? In what order should I introduce them since they grow at different rates? Im guessing they shouldn't all start at once in the 125 if I get each species around 2". If another combo is better I'm very open to suggestions. It's the Severum(s) that I definitely want in the equation.