If you need even a bigger logo (120px), then you have to change default column grid of the header. As you know (?) in all Helix-based templates is based on bootstrap columns. In that template logo column has only "2" (desktop) and menu "8" (desktop) and top3 also "2" (desktop). In means to get wider logo, you have to reduce menu width from 8 to 7, and give that extra 1 to logo column. Simple bootstrap math rule based on 12 grid.
Check Layout settings, and made above corrections. Or create your own custom header.
And yes, you can keep suggested by me CSS anyway.