The essesse is the older model. Until they brought out the Turismo & Competizione models, all you could buy was the basic 500 which if you wanted more power from you bought the Esseesse upgrade for.
Standard 500/595 gets 135/140/145hp and comfy suspension.
Turismo gets 160/165hp, intermediate suspension (FSD on the front) & more luxuries
Competizione gets 180hp, hard suspensions (FSD on front & rear), bigger brakes and (unless spec'd otherwise on the very latest models) chronically uncomfortable Sabelt seats.
There are also limited run versions such as the Trofeo, Yamaha, Ferrari & Rivale.
Elaborazione kits exist to upgrade Standard > Turismo > Competizione (effectively a rebrand of what the Esseesse kits offered before).
Or you can take your car to Tune4Performance in Watford and get Tony to upgrade it for a fraction of the cost.