i tested my sound system on my x3 today, I think sound is very reasonable, for most people they would not need to upgrade to Premium sound. use that money for other packages. HUD is nice but really not worth the money, I had HUD on my Pontiac in 1998 so it not such a big deal really. I think after Premium and technology i would add M sport and CWP. that should do it on X3.
2014 328 GT Msport, Mineral Grey, Premium Package, Tech. Package, CWP, DAP, Lighting Package, HUD, Harmon Kardon.
2013 328xi Mineral Gray, Moonroof, CWP