Although I am no expert... I believe the best scanning sensitivity has a direct corolation to your budget.
My x800xl has the XT PE core. I paid 140$ cash for something that was, at the time $400+...
so i understand the immense value of my find... so i keep my sensitivty to the highest possible.
If your card can be easily replaced... then maybe you can afford some artifacts.
Your call mate... how much cash do you have to 'Burn' ?