SV650.org - SV650 & Gladius 650 Forum - Do I need an amp for 6x9's?

If you want proper oomph than an amp is the way, i used to be in car ICE quite a bit so know a fair bit.
Dont know bout now, but decent speakers used to be sold in component form or as 1 unit, but you must make sure they are designed to go in your parcel shelf into 'free air' (thinks thats the correct term, its been a while) or they wont get the sound they have been designed for, in other words, in a pod to a certain volume of air or free air as in a big boot full of air.

A half decent 2x50 amp would drive them nicely, the rule of thumb when i was into it, the head unit played the music, thats it, amps gave it the power.
In my mk2 golf i built some fibreglass door pods with JBL component speakers and a JBL amp to drive them.
If you want bass though mate, there aint no replacement for displacement, in other words, you gotta go big.
For punchy bass a 10 inch sub is perfect, for nice all round low sub vibes then a 12 inch, if you wanna rattle everything on your car than a 15 will do that nicely.
You could easily square off a section in your boot and fit a 10 inch sub, the manufacturer will give a recommended volume of air for the sub / box which to check you can fill with polystyrene balls and measure it so its close.

HTH