Forget the 75db reference settings. Let's work with what we have to get what we want.
Room: 15'x22' w/cathedral ceiling 11' t0 16' H (22'L) ttl. room vol. 4,800 sq.ft. (flr. carpeted)
NO going for sweat spot. Looking for great sound through-out room. 2ch, or DSP 2.1 or 5ch STEREO.
Dolby PL 2 music surround sounds pretty good, BUT...
SYSTEM: Onkyo TX SR353 5.1
Spkrs.: Pioneer SLF3 F & CR (ttl.spkrs.=10) Sub: Yamaha YST SW 012
Set-up: L & R elev. 6', 10' apart, 3spkrs each side, standing vertical & arranged slightly articulated
Center: 2spkrs elev. 6' RR & LR: 1spkr each side, elev. 7', 12' from front at 90 degrees.
Sub-woofer: 3" off floor, 2' from back & 3' (ported side) from side wall. VOLUME set (0-10) 7
Run Auto Set-up with MIC to establish parameters CENTERED at 5' elev. 12' from front. Switch to MANUAL Set-up to tweak.
Final Settings for MUSIC: Speaker Levels: L -6 C -12 R -6 rr -8 lr -10 Sub -3.
With ALL Channel Stereo rear volumes adjusted DOWN to keep sound stage in front yet bring sound 'out' into room. Warmer sound with center OFF. Master BASS +10, TREBLE +2, volume can be any level you wish. LOUD & CLEAR! You can be within 4' of woofer and not 'SEE" it. Having levels low and volume up is harmonic bliss when done right.
FYI: try this setting with itunes: open EQ, adjust pre-amp down to about a 1/4 or less. Adjust graphics to FLAT. Adjust 150db bar to bottom or almost bottom. Plug in your Bud's or Can's and get ready. WoW! even inexpensive bud's can sound pretty darn good.
Play with this. Experiment. Adjust your pre amp and pre levels down while maintaining harmonic presence and turn up main volume. It takes some getting used to. your listening level may go from 30 to 45 to achieve same volume but clarity will amaze you.