Thanks for all the replies and advice. It helps to hear others have had similar issues.

I'm going to play some more with it today. I'm going to increase the 990 receiver's subwoofer output level to around -5 dB (for comparison, my front left main is at -2 dB) and drop the EP500 volume control down. I also think I'm going to calibrate the subwoofer level a little higher than 75 dB on the SPL meter. I know that the SPL meter isn't reading the actual subwoofer level at such low frequencies, such that a reading of 75 dB actually indicates a higher real SPL level. But I don't listen to things too loudly and feel that I lose the subwoofer at lower listening levels. I'll try and calibrate it to 80 dB on the SPL meter and see how that sounds.

Is there any concern setting the EP500 amp's volume level down to between 4:00 and 6:00?

BTW - I haven't played around with the Full/Half settings on the EP500 amplifier? Do these make a big difference? I might try these out as well. I might also play around with different locations for the sub but I'm somewhat limited in placement.

Thanks again!