You can usually hook up to six speakers and a subwoofer (6.1).
Most computer speakers with subwoofer have the power going directly to it, so it is needed to get an extension for all the other speakers.
If the receiver is just stereo, not surround sound, you will not be able to create a surround sound (front, centre, sub, surround) setup.
The home sound system should have multiple HDMI inputs. It must be able to send amplified audio to at least five speakers. Also be aware about the system if you wan't the 5.1 you have three speakers, two surround speakers and a subwoofer. In 7.1 you only get four surround speakers.
Ideally, each speaker in a set reproduces a separate audio channel. If you want to listen to two-channel stereo recordings from your AM/FM tuner or CDs, you'll need left and right stereo speakers, available in a variety of sizes that project sound in front of a listener. You can purchase additional speakers to experience the magic of surround sound and thundering bass while watching movies.
A used Cerwin Vega Subwoofer can be purchased from sites such as eBay. It can also be purchased on sites such as Gumtree and Craigslist. They can be hard to find new so are popular second hand.
4" fronts. You would need to get some 4"T speakers for the fronts unless you want to do a little custom work, and even still, you may only be able to attach two mounting screws. In the rear are 5.25" speakers and a few '91 4Runners had a tweeter as an option in the rear corners of the vehicle.
the subwoofer, i believe, is under your passenger seat -- move the seat all the way forward and you'll be able to see it from the back seat (rear right side door opening, that is). the layman's way to figure out if it's working is to play some music and rest your hand on the subwoofer -- does it vibrate with the bass?
depending on the year of your legacy you should be able to access the rear speakers from inside of your trunk.
Maybe. If you need to drive passive speakers, you will need an amplifier. If you have powered speakers, you might not be able to control the volume of the signal.
For professional speakers you could try your local music store. If you don't have any of those, you might be able to purchase a nice set of speakers from Amazon and the like.
Speakers are the weakest link in any audio system. Always buy the BEST speakers you can afford. You won't be able to hear the difference in lower priced electronics but you will in lower priced speakers.
Floor standing speakers are good for a number of reasons. They are larger than wall mounted speakers and are able to contain additional speakers that change the sounds and make it more pleasurable to listen to.