speakers for the 72?

[125]

the speakers in my truck are old and junk, and i need new ones, i was thinking of getting some off ebay, some 5 1/4 2 ways or something like that will do

i guess i would need an amp since the head unit is only putting out like 20 RMS watts....how would this work?...50x4 cd player - amp W? - speakers, would i get a 200wx2 amp or somewhere around there?

also does anyone know if speakers are measured by their outside diameter (the cover) or the actual woofer.....i just pulled one out of the truck and the outside is 5 1/4 but the mid woofer is only about 4 inches and i cant fit any bigger than the ones i pulled, unless i take them out of the kick panels and go to 6x9's and stick them in the doors (ill need to get a new drivers door before i put speakers in the doors or if i do....its rusted out on the hinge and keyhole)

6x9's
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5711253357

5 1/4's
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5710554381