not 100% certain but i dont know of any stereo's that you cant add a subwoofer too you will however need a power amp to drive the sub.
Of course!
Yes, most cars come with extremely basic factory installed stereos with radio capability. Factory installed car stereos have changed over the year. The quality and features of the car stereos differs between manufacturers.
Cheap car stereos typically have very low bass and lack the "bump and thump" of more expensive car stereos. You can purchase nice car stereos online from websites such as Amazon, Best Buy and Walmart.
One can purchase car speakers and sub woofers from most car accessories stores including Halfords. They can also be purchased online at Argos and Amazon.
clairon
The users reviews of Kenwood branded car stereos have been very good. Most of the reviews state that the sound on the stereos is of good quality, it has many features and is easy to install.
Truly, the best car stereos have clear, non-muddy bass, and crisp treble. Ask your car stereo dealer what he thinks, and he will usually give you an honest opinion.
Walmart probably has some of the cheapest prices on car stereos but price doesn't translate to quality. Crutchfield has some amazing deals on car audio equipment.
No, but it is nice if you want to play loud music.
Craig's List or Ebay
ground it to the body of the car floor board
There are many different brands of car stereos. Some of the more popular brands include: Pioneer, Boss, JVC, Kenwood, Alpine, Sony, Fusion and Clarion.