New excavation business equipment selection

Hi I am new to the forum. I live in central NJ and I have been trying to grow my excavation business over the past few years. I currently own a used cat 289c with a 4in1 bucket, flail mower, forks, and gp bucket. I just bought a used f750 hook lift. I also own a 12 ton econoline deck over trailer, and a 7 ton drop deck trailer. I currently do mainly small excavation and drainage projects with a rented 5 ton excavator. I would like to grow the business to include doing septic,foundations,and additions. I would like your opinions on what size excavator would be best for my business. I know the 5 ton capacity and what I can do with it pretty well.

Thanks in advance.

New excavation business equipment selection