Given the current build of our roster, we really have 2 holes in the top 6; one next to Horvat and Barzal and one next to Nelson and Palmieri. As far as I can tell there's no money to bring in a tested top 6 player and there's no way to trade for one without robbing Peter to pay Paul. So those spots will go to two of these players (in descending likelihood):
Holmstrom
Tsyplakov
Iskhakov
Wahlstrom
Maggio
Gauthier
Dufour
This is why if you think Mcgroarty is NHL ready you have to find a way to get him here. You can slot him with Nelson and Palmieri, Tsyplakov with Barzal and Palmieri, and keep Holmstrom on the 4th line where he probably belongs without adding to your cap hit.