Just to add a quick remark about the surround speakers - they're supposed to provide more diffuse, ambient sound (as opposed to more directional sound for the Front/L/R speakers), which is why the recommended placement is above ear-level.
AVRs with auto-calibration can adjust for speaker distance and volume levels at various frequencies, but it can't compensate for a speaker firing directly at your ear when placed close to ear-level, hence the recommended speaker height placement. I initially had my surround speakers placed close to ear-level, then raised them about 18" when I found extensions for my stands - I definitely noticed a difference.
AVRs with auto-calibration can adjust for speaker distance and volume levels at various frequencies, but it can't compensate for a speaker firing directly at your ear when placed close to ear-level, hence the recommended speaker height placement. I initially had my surround speakers placed close to ear-level, then raised them about 18" when I found extensions for my stands - I definitely noticed a difference.
