I took my new Tacoma truck to a Stereo Installation shop. They offered to install amp's, comp. speakers and a sub using the the stock head unit. They suggested it would sound just as good as an aftermarket head unit. Is this true? What are the advantages/disadvantages.
They are being dishonest in my opinion. Almost all stock headunits do not have pre-amp outputs so they would most likely use line out converters from the factory speaker wires to get a signal to the amps. This is going to make the sound a lot less life-like and static-filled. Also, you want to consider the fact that many aftermarket headunits offer better soundshaping control, especially over the subwoofer when compared to that of a factory deck.
The only advantage, however, that I can see to retaining the factory unit is to maintain the look of the interior if you do not want a flashy aftermarket headunit.