all right, if u want an option, pick up a 5.1 reciever, if you just want volume any brand will do ; however if you want quality a brand name should be better....
hook up the reciever as a pass through between your sound card and your speakers --- bingo --- very loud system.....
you'll then notice just how crap your logitech speakers are -- good thing is you can add more speakers as the logitechs are powered on their own and only require 1 output -- you can change the fronts / sub separateley