imo it's most important to have a top class (i.e. top 5 players in the league-class) midfielder; whether that's an import or an Aussie/Kiwi.
A-Rod and Gui aren't at that level.
With Roly gone, we've lost that - I don't think spending that import spot on a RB will propel us to top 4.
Roly had one good season with us and that was when the team was firing around him. Who knows how Gui or A-Rod (who is a couple of years older now than he was then) would fare with the same sort of team.
Edit: Actually, we do know with Gui. Although he is getting on he is a class player.