Thanks to mdrew and jakeman. Your inputs point me to the right direction I should pursue. It's very helpful, believe me.
Now, to give you some more details:
All 5 in-ceiling speakers are made by Speakercraft. FR at +/-2dB is 38Hz-20KHz. I used the test tones from my Yamaha RX-V1500 to calibrate the speakers and EP 600. I fixed the receiver's master volume control knob at zero (0 dB) as the reference point, and adjusted the speakers trim level from +1.0 to +3.5 to get me a reading of 75 dB on the SPL meter. For the sub, it registered -10 dB on the trim level and 78 dB on the SPL meter (The sub volume is set at the 7:00 o'clock position). At these settings, I hear no explosions, no poundings coming from the hoofs of the giant elephants in the LOTR's ROTK. Out of luck, I managed to get some good sounds when I adjusted the sub's trim from -10 to -5dB (remember, this is my first time to do this calibrations).
My speakers are set to "small" and receiver crossover at 80 Hz. EP 600 crossover is "bypassed". Sub volume at 7:00 o'clock position.
