no, you dont need a subwoofer unless you want low end bass.
four options:
2.0 pc speakers
2.1 pc speakers
2.0 powered hifi
2.0 unpowered hifi
hifi is going to sound better than pc speakers but will cost a bit more and you will not get a sub for that price.
going unpowered passive speakers with an amplifier gives you more choices for speakers but eats up a bit more budget.
good speakers to pair with an amplifier: pioneer bs22, micca mb42
good powered speakers: pb42x, cr3,