I've seen enclosures for 6x9s, and Ive heard about people using them, but a lot of cars come stock with the rear speakers just open in the trunk. and when i go into circut city (or wherever), usually the working display speakers are just mounted on a wall with an open air room behind them
so do 6x9s NEED enclosures? or do they just help with the sound?
No, 6x9's are usually optimized for free air (open in the trunk) use. They don't usually help the sound out. I'd put 6.5" midbass drivers instead of 6x9's in a rear deck, then focus on a good component system up front.