Expedtionay force series by Craig Alanson is fun romp around the galaxy. The start in first book is a bit slow and the tone of rest of series is very different.
Lost fleet by Jack Campbell is nice as well. Its more about fleet action and battles.
Terran Republic series by Charles Gannon is also quite good.
Icarus Hunt series by Timothy Zahn was very interesting.
Good suggestions. I've read the first three in your list. Liked Old Man's War, was neutral on Expeditionary Forces (but still read like ten books so...), and didn't like Lost Fleet.
Haven't read the latter two series though, so good suggestions! Got a short synopsis for either of them?
Terran Republic series is about Earth fianlly meeting some alien races after it had expanded to a handful of planets. There is lots of politics and maneuvering among the races and earth is kind of caught in that. A secret org on Earth tries to guide earth through all the mess and the protagonist is recruited into this org.
Icarus hunt is about a pair with an old spaceship (Icarus) being hired to take some cargo to a different planet. However, major corps and races start looking for their ship trying to get hands on the cargo.