Now i can hear a good bass in stereo mode by doing changing in settings. I have override all the settings done by Auto Audyssey Setup.
Setup in AVR
Front Speakers are set to SMALL.
Bass Settings : LFE + Main
Subwoofer Volume: 0dB
Subwoofer Crossover Frequency : 80Hz
Front BS Crossover Frequency : 60Hz
Center Crossover Frequency : 90Hz
Rear Crossover Frequency : 80Hz
Speaker Setup : A
Subwoofer volume is set 12 Oclock position.
subwoofer frequency knob at Full open
Phase : 0 degree. (I can't hear any difference by switching to 180 degree).
What i have understood is Aviano 2 have a frequency response of 45hz - 20khz. I take that to mean that any frequency under the 45hz will not be reproduced by the speaker. So the AVR should have the crossover frequency for that speaker set to 50 -60hz so that 50hz and lower frequencies will be sent to the sub to be reproduced.
As Sunder suggested, set the front BS crossover to 80.
Also, set the subwoofer crossover to highest, could be 120Hz. Subwoofer crossover is for the LFE channel (.1 channel) which can go upto 120Hz. If you cross it at 80, then sound between 80 to 120 for .1 channel is perhaps lost.