I am one of those insane people that has FOUR subs, including (two) EP 500's in a room 28' x 12'. Of course I started out with two subs a few years ago and added the EP 500s a short time ago.
I did this to smooth out some room anomalies but not necessarily to add more SPL. Like Jim Logan, I was very limited to my placement options as well, but once I did my volume AND LFE balancing and made sure phase was in order everything turned out fine and it is not overpowering despite the power available to me.
I have found there are a couple of options out there to improve subwoofer sound, one expensive and one not. The ideal is a Velodyne SMS-1 digital drive equalizer system (which I have) although not perfect, gives you considerable flexibility in your subwoofer set-up options that you don't have by itself. Unfortunately, it is $600 bucks. The other option is a GRAMMA platform which is primarily used for large musical instrument speaker cabinets to get them off the floor in not so good acoustic environments. It is made by Auralex Acoustics and is available in a lot of musical instrument stores for between $50-60 dollars. Depending on whether the sub is on a bare floor or carpet, it helps take away some of the boominess. The EP500
tends to be a more linear sub than most, so the problems that are being discussed really should be correctable one way or another.
