you have an Amphiprion Percula clownfish, picasso type. Hence, you can pair it with any true percula clown... meaning another picasso, platinum, onyx, regular true percula or even snow onyx clownfish which is a hybrid of snowflake (Ocellaris) and Onyx (Percula).
As to you grading question, I avoid the term extreme picasso. To me they are either Premium Picasso like yours or Semi-Picasso with more orange. You could technically call a platinum clown (all white) an extreme picasso because its genes came from picasso clowns. Hence, I do not favor the term. That said, not all Premium picasso clown are created equal. Some are more white than others, and have "cap" on like yours. Others either have normal head and face or have a "helmet look".
This is somewhat recent addition to Designer clowns. They are called Nebula clownfish
http://www.liveaquaria.com/DiversDen/ItemDisplay.cfm?c=2733+3&ddid=320783