I grew Apex and Lilac Diesel - both really pretty, Lilac a bit more potent but the terps on Apex were among my favorite to smoke. in relation to potency, I found them neither low or high, just average to solid (i have only grown 5 apex and 5 lilacs but have smoked lilac from another grower too).
I hear some growers in the forum mention that Inzane in the Membrane (sold out) and Mandarin Cookies (still in stock) to be among the best for potency.
Mandarin Cookies is probably one of the flagships. I ve seen good reviews on Cherry Garceeya as well.
There is a thread in relation to the Ethos Club Members here in OG, they might be able to tell you more about potent strains by Colin.