dont use realjuke box.. infact, delete that and never mention it again.
itunes will work fine, you prolly got volume leveling or boosting on which is unneeded. you have itunes set as mp3 or aac? doesnt really matter altho i prefer mp3 because its compatable with everything, aac is more of apples own format.
you honestly dont need 192, i usually use 160, 128 is the 'normal' that most people use. However thats not your problem. i'd try and check to make sure any volume leveling or editing is off. also, sometimes some people have the volume on the computer turned down, then the volume control on the external speakers cranked to make up the difference and that never sounds good. it should be the opposite, computer volume level turned up 100% and all control done with external.
if you want other mp3 encoders, theres many good free ones you can get. personally i use Winamp, i like it better then itunes because it can do VBR mp3's while itunes cant.