The only reason I could see for getting the Logitech's over the Gigaworks would be if you wanted the extra digital goodies. Other than that, the Gigaworks has a higher SNR, broader frequency range, and BASH amp on the sub.
BASH is a good thing because of the non-conventional way in which it amplifies a signal. To save you the long defination, BASH makes use of switching individual amps on and off to lower heat production signifigantly, allowing for more power output and greater efficiency.
The upgrade form your current setup will offer bass that will blow your mind. The Inspires are a decent set, but they are lacking in bass response and have lots of distortion most of the time. You'll also have clearer vocals, especialy in lower male voices, due to the increased power and higher quality for the satalites. If you can afford to part with the extra dough, the Gigaworks will treat you very well.