Guys, I wanted to check in with regards to the Onkyo 674 receiver.
As an owner, I wanted to report that I found no 10db boost issue using my PS3 as a Blu-ray player. I felt plenty of rumble from my HSU Subwoofer, and the volume knob on the back of the sub was @ 12-o'clock.
However, after hooking up my new Toshiba HD-A2 HD-DVD player (via HDMI) this afternoon and playing the Mission Impossible 3 HD-DVD, I immediately noticed the LFE level was severely low (especially for a title as explosive as MI:3 is). So I immediately raised the Subwoofer level on the Onkyo speaker setup to +10db and now everything is fine.
So to recap:
The Onkyo 674 has no apparent 10db boost issue with Sony's PS3 as a Blu-ray player.
However, using Toshiba's new HD-A2 player, you have to raise the Subwoofer channel +10db in order to receive normal LFE listening levels.