Gattuso > Inzaghi, not even close. The latter is a stubborn and inflexible choker, stay away as far as possible.
However, we absolutely need to hire a top coach: ZZ or Max. Sell a player to fund it if needed, couldn't care less.
We need a proper coach first and foremost. Then it's possible to do it even with a lesser squad, the other way around it just doesn't work. You could give prime Real or Barca to Pirlo and he'd have bottled it somehow.