depending on type of music and intended volume, an amp is definitely a good idea, but adding a sub woofer might do well too. You will need an amp or two if you are looking to drive all those speakers. I would use a quality amp for the speakers (don't buy the cheapest; JL is great but a bit pricey, Clarion is also a good but not so pricey), the sub amp (mono channel) does not need to be expensive just have the right or adequate power. it operates in the lower frequency range only, so hi-fi quality is not going to be heard here nor noticed that you spent oodles.