head unit install no sound??

ok i got an alpine cd player and i have the factory bose system in my car. hooked it up and there is no sound. i understand that i can buy an adapter to make the speakers work with the new deck install and i dont have to change all the speakers. i just want to know if it is worth it and if it is hard to install the adapter. where is the cheapest one i can get? any help is appreciated.

the adapter just gets wired up to the car like you did the deck, then you wire the deck up to the adapter, then adjust the sound levels if it has those controls on it.

i've heard mixed reviews on the sound quality using similar adapters.... anyone?