You have no installation manual? What type of audio or sound card are you using to drive this new sound system?
Yikes, no wonder you are having trouble. How many colored plugs are there on your sound card facing the back of your computer. What colors are there? Red, Yellow, Orange, Green, Blue, and Black are on my HD Audio panel
See if this helps you:
5.1 speaker connections
Okay great... glad you got it working
Max sound depends on the amplifier/ subwoffer. With systems like yours, the amplifier is in the subwoffer case
some soundcard has higher output so by upgrading you may get higher volume. and yes when you turn the computer volume to max and your genius speaker to max, that's the highest volume you can get.