Back in the day, we had 2 channel amplifiers because we used passive crossover networks. Then the powers that be came up with a neat idea.....a 4 channel amp! These were very popular in the 90's but they needed more power for the subwoofer systems, so the sub amp was created in the 90's as well.
Evolution took a few more turns, requiring more channels in one footprint, so the 5 channel was created. This has been the most popular style of amp for many years.
Manufacturers came out with multi-channel amps, so to upgrade these monsters, more channels were required in a single framed amp. 6, 8, 9, 10, 12, 14 and even 16 channel amps are available. Here is what SoundsGood Auto offers....
Vendor:Hertz