[After I get my WRX wagon,] I was considering just buying the sub-woofer without the upgraded speakers. Then, I would buy Infinity 6.5" 2-ways in the front, and either 4.5" or 5.25" 2-ways in the rear. My main concern is whether the stock HU has enough power to do justice to those speakers. I would like to avoid adding an amp or replacing the HU. Do you think they will sound okay without additional amplification, or am I better off just buying the upgrade speakers?