Need recs on a really good LOUD speaker set to hook up to iMac

Building a house and will have a music room for guitar, drums, etc. Have an iMac to play music, and will need a good set of affordable speakers. In the past those 4 speaker/subwoofer sets have always sounded distorted when turned up too high. Right now, I'm using one of those sound towers, but it doesn't go loud enough. I also don't really need 4 speakers, but do need a subwoofer either separate or built in. Thanks!