Anbu are jounins that specialize in a certain field,that being Leafs top squad.Kabuto is stronger than Kakashi imo,he pretty much was beating the shit out of Tsunade,and she is hokage.If Kakashi was near such a strength,why wasn't he even considered for becoming the 5th hokage.If you've only watched the anime so far.then you have reason to believe he is strong,but he really isn't.Itachi tossed Kakashi away like Kakashi was tossing Naruto in the Genin exam.Maybe that was being too generous,he wasn't even worth Itachi's effort,not like he put any in on jounin like Kakashi.