If I read your original post correctly, you want to run a line output from your head unit to a crossover then amp(s) then speakers, thats the correct signal path. Like I said before, for every frequency range you are dividing (splitting) out of the crossover you need an amp channel to drive that frequency to a given speaker. A three way crossover would handle subs, mids and highs. If you went with a two way crossover you could run your subs then mids but you would have to use resistors in line from the mid speakers to the tweeters to eliminate unwanted frequencies. In either case you need to check the specs on the 6.5" speakers to make sure they will go down to the crossover frequency where the sub frequency tops out. Sorry im not trying to be a jerk but unless I read your post wrong, all those who told you it would work are wrong. What I would suggest is a 3 way stereo crossover with a 4 channel amp for mids and highs and use your current amp for subs. The subs do not have to be in stereo, mono is fine. Hope this helps.
