Depending on what you're listening to, most music is encoded to be listened to in two channels. A left and right speaker are capable of recreating the entire soundstage. A sub helps when the L/R can't reach the lower notes without compromising the mid and high ranges. This will almost always be best for listening to most music tracks unless they were encoded for multichannel listening (SACD, DVD-A are some examples) That said, I sometimes don't mind using PLIIMusic or some other DSP mode. Its up to your processor to decide what material will be played by the surround speakers. Back in the days of ProLogic, it was done strictly by frequency, other DSP modes work in various ways.
I would stick to 2.1 in your case, especially when listening to something as wonderful as Norah Jones. You should be able to set up those speakers to create a very realistic soundstage in front of you.
