Hansang, What did you do to the XA2 to get the bass back? I have a toshiba A2 and I am using bitsream for the audio I think.
Unfortunately, it won't help you since you are using HDMI/bitstream. My SR8001 can't decode HD Audio so I use analog outs. I used to use HDMI/PCM, but bass/LFE was really lacking. I then switched out to analog output on the XA2 and analog inputs (AUX2) on my SR8001. Then did what it said in this first post: http://www.avsforum.com/avs-vb/showthread.php?t=856083