[Gorthaur the Cruel]

So we all know that the Istari were Maia from Valinor who were trapped/imprisoned by the Valar in incarnate forms of old men, so as to prohibit direct displays of power and splendour. And in these forms, they were subject to the frailties of the flesh (weariness, temptations, etc..). But they also had great powers of mind and hand (?). But in terms of available power (since the Istari were powered-down maia), how would we rank the Istari to someone like Lúthien Tinúviel, who seemingly had a larger grasp of Magic/Power (obviously derived from her mother and her elvishness)?
And what of Melian? Did she not also become incarnate so she could birth Luthien? Is she bound by the same consequence of Elven women diminishing in spirit after giving birth? And because she became incarnate, she had a power over the substance of Arda. Now would this not apply to the Istari, as well, that spiritual beings gain more power when incarnate?

So would y'all say Luthien was more powerful than the Istari? And if so, in their diluted states, would they also be lower in power than the remaining big shot elves left in Middle-Earth by the 3rd age (Cirdan, Galadriel, Elrond, Glorfindel, Celeborn, Gildor, etc..)?