Is it like a hum or is it like static? If it is like a hum it is probably a ground loop, created from a difference in potential between the two outlets you have those units plugged into. You may fix that by trying to keep them on same circuit, and if that doesn't work, use a cheater plug (a three prong to two prong that disconnects the ground wire).
If it is a distortion, it might be the input levels are getting too low when you split the signal like that.
If I were you, I would get an inexpensive receiver and some inexpensive speakers to run off it. Run one pair of speakers for your games off the B channel, and the main/A channel can be used for your music (pre-outs for your powered monitors).
I can't find your EQ online, do you have a link?