pro tools express with imac

Hi!



I am going to upgrade my windows 7 to an imac.



And I really dont know what operative system to choose, any one who can give me a tips.



I have used the info on avid sites and it said that i can use mac os x from 10.7.4 -----10.8.3.



And imac 21,5 inch , 27 inch late 2012?



will the operativ system mountain lion work? and what about maverick as I have seen that these are the two operativ systems imac comes with:=)



Thanks!!



Cath from norway