What is the difference between this mouse and the G903 Lightspeed? I ordered a set with the G903 Lightspeed and the POWERPLAY. My mouse has a problem with a button and I would like to use the same one. I've ordered a set with the G903 Lightspeed and the POWERPLAY mouse pad, and I'd like to use the same one. But I see that this version is cheaper and available immediately, unlike the Lightspeed version which will only be available in 1 month.