would aftermarket speakers?
if you get good aftermarket speakers theywill be alot better than your bose's bose makes good home audio but there car audio is not very good if your looking for speakers some brands i would recomend are Focal Diamond Audio MB Quart Boston Acoustics Alpine(well the Type X) Infinity JL Audio and Memphis
yes i own a gtp with the bose system and replaced the 6x9's and yes it sounds alot better
it depends if u get like infiniti or sony or if u get a generic ones its pointless. the stock ones are always better