I have an Onkyo TX-SV727 Spec
POWER COMPONENTS: Dual 6,800 uF Capacitors, Over-Sized Isolated High Power Low-Impedance Transformer and Extruded Aluminum Heat-Sink, which effortlessly drives 4 ohm loads
POWER OUTPUT: 100 Watts RMS x 2 @ 8 ohm/ 130 watts @ 4 ohms
Frequency Response: 20 Hz – 30,000 Hz
THD: 0.08%
Signal to noise ratio: Tape/CD 100 dB, Phono 80 dB
Phono: MM output 120 mV
Damping Factor: 60 at 8 ohms
Adjustments: Bass, Treble, Balance
Selective Tone Control
Six Class Classifed tuning
Local/Dx auto/mono/Automatic Precision Reception (APR)
Audio Input: Phono, CD, Tape 1, Tape 2, Video 1, Video 2
30 AM/FM Presets
Impedance Selector: 8 ohm/4 ohms switch
Speaker Connection: Clip-Lock – A, B, A & B 4 & 8 Ohm
Dimensions: 18" W x 13" D x 5 7/8" H (45 x 331 x 150mm)
Weight: 20.9 lbs (9.5 kg) without packaging.
Hooked up to MX-250 Cerwin Vegas which are 4 Ω. Does the receiver know the resistance or is there a way to select it? And what can I do to optimize the system?