back shelf help

[~ Joe ~]

right im in the process of looking at / getting a new head unit, door speakers / tweeters and some new speakers for the back shelf, i was going to get some 6x9s but i was told that there is no point and its better to get some 3 way 6 1/4 speakers...... is this true? if so what speakers would you recommened to go on the back shelf ? should i just get the 2 or go for more? or should i get different types? ill be running the door speakers and tweeters off a seperate amp whilst the speakers in the shelf will be run off another sub in the boot