As others have stated, a good AVR should not much up the HDMI signal, and it makes for a neat wiring solution. Run all your HDMI to it, then one out to the display, and enjoy lossless audio.
After you cut off any AVR processing, you can easily check to see if it is doing anything to the signal. Buy the Spears and Munsil disc, first check the results of the patterns with your blu-ray player running directly to the display, then check the same patterns with the player running through the AVR.
65" VT50 / BDP-S6200
X4000 / Outlaw Model 7125
Klipsch RF82 II and RC62 II / Hsu VTF-15H (2)
Directv HR44-200 / HR24-500