good brother i use same sbs 5.1 in 2003 it is very good ..
but there is a simple thing to understand.. In home appliences and car electronics there are some differences.. When the manufacturer creates something for car :
it should be Heat resistant
It should be stable on different Voltages
it should be water vapour resistant upto some level
and its construction should be solid and it should be Jerks resistive
on the other hand home appliences dont have such characteristics , duo to that its prices are almost 5 time lesser than car electronics.
yes you can use this into your car . but it will stop working after some time . . rust .. power issues.. breakage are the issues..
any way keep exploring and best of luck..