when the actual characters of the manga believe hes at kage lvl, it means hes at kage lvl.. regardless of what we think of him.. he fought pain w/o info on him.. although he got pwnd, i'd say he did pretty well.. lasted pretty long, and impressed pain enough for him to "dispose" of him asap.. and even if you think hes NOT at kage level yet, i think that once you are a kage, you're allowed to learn forbidden jutsu's.. a man of kakashi's calibur with forbidden jutsus.. would that not be kage level enough?