It doesn't usually take much, because very few cars or TVs come with powered subwoofers or 6x9s or quality tweeters. Second hand amps, receivers, etc. are usual

It doesn't usually take much, because very few cars or TVs come with powered subwoofers or 6x9s or quality tweeters. Second hand amps, receivers, etc. are usually a good deal, entry-level speakers are pretty cheap new though.