An interesting point though, I couldn't connect both subs via the subwoofer out on the receiver. I got a bad hum through both subs when connected with a "Y" connector. So I hooked one up via the high left channel. So it's curious to have the dedicated LFE, and have the second sub firing the strictly the left channel bass. Made for an interesting gaming experience.
Were you connecting both subs to the same outlet? That hum is a ground loop, and is being caused by some issue with your house's wiring. If both subs on are the same breaker you shouldn't get the hum though.
