If you buy a good set of tweeters, they will come with xovers,other than that, you will need blockers for the tweeters,or they will fry!Your amp should see a 2ohm stereo load ,provided that the 6x9,and the tweeters you choose are both 4ohm.My Kicker KS25 tweeters just came in today to replace my Infinity 8yr old Kappas:naughty: