i have had my Z5500 for over 2 years now they would have to be the best speakers i have spent my money on they a perfect for gaming movies you name it, i have had my speakers at only half not cos they cant handle it but my flat starts to move around lol but i have listen to them at full a my local Computer store and boy most speakers just die or sound like **** but these kept there clear sound the whole time.
now for the creative gigaworks s750 these a ok but i have also listen to these useing the very same sound card and these speakers started to lose sound around half Vol, and we do have ppl bringing them back cos they have blowing the speakers if i was you i would go with the Z5500 they hands down beat the creative gigaworks s750 for both gaming and movies it makes sence to go with the Z5500 you going to pay $200 less then the creative gigaworks s750 if they a better then the Z5500 it's in placers that dont even matter or you would even notic
the Z5500 hands down a the best speakers you will ever get till they bring out the new logitect speakers which will blow these babies out of the water but be warned get ready to pay $1500 + for them as i do work in the Computer Store i cant Blow my mouth of and tell ppl what there name is as i will lose my job but all i can tell you there a 7.1 version of the Z5500's.
Hope this helps goodluck