Thanks a lot for the warm welcome. Its nice to have a support community like this.
I have checked & verified the speaker wire polarity & HF-LF connecters. They all seem to be fine.
My media room is a 3 car garage (30 feet * 25 feet) . So, there are lots of hard surfaces (garage door, concrete floor etc.). So, naturally there is a lot of echo in the room. Disabling the Audyessy XT calibration seems to help. I switched to manual EQ & increased 63Hz - 120Hz frequency range to the max. My denon receiver is not showing options for frequencies less than 63Hz. I also increased the bass tone to the max. Its better now but its still not enough. I am sure 280s can produce more tighter bass.
Since my surround 160s seem to be producing more bass, naturally the places close to 160s seem to have decent bass. But as I get closer to 280s, bass dies down.
I am relieved no-one mentioned that the receiver's power output may be the culprit. My test music is not of very high quality. I am playing via airplay. I am waiting for my projector still. I wonder if thats one of the problems.
Any other ideas are welcome.
Thanks a lot guys.