What should be my next extreme demon?

Basically title, the context is I've beaten 7 extremes with two of them being around the same difficulty as my hardest being Blade of Justice and Sapphire Angel (which i beat yesterday :P) these two are ranked around ~600 on AREDL so im looking for a new hardest from i guess top 400 or something? Im not sure how much of a jump these become the closer you get to the top of the list haha