ignore such descriptions as "360 degree audio" as the sound waves will bounce off the walls anyways. such descriptions arent entirely accurate nor relevant.
instead think on these two things:
do you want stereo (2.1) or surround (5.1) in your speaker system?
do you want (possibly) better speakers or more speakers?
keep in mind that movies are usually in dolby surround sound, except some animation which is stereo only. games are usually surround sound, except some older games which are only stereo or mono. windows sounds and internet (youtube etc) sounds are all stereo or mono. most music is stereo only.
i've had the $100 logitech 5.1 sets in the past and they have been a good value for the price paid. not top end by far but definitely good enough to always recommend logitech.
i've also heard logitech 2.1 speakers, albiet the $50 model, and they also sound good for the price. not sure how much (if at all) better the $100 model sounds over them.