I would go for a Denon, Marantz, Yamaha, or Pioneer in the same price range.
Personally I prefer Denon.
From HTM on the 551R:
Two channels driven continuously into 8-ohm loads:
0.1% distortion at 95.2 watts
1% distortion at 111.3 watts
Five channels driven continuously into 8-ohm loads:
0.1% distortion at 68.2 watts
1% distortion at 81.2 watts
This graph shows that the Azur 551R’s left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 95.2 watts and 1 percent distortion at 111.3 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 118.6 watts and 1 percent distortion at 139.8 watts.
THD+N from the CD input to the speaker output was less than 0.008 percent at 1 kHz when driving 2.83 volts into an 8-ohm load. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –85.52 dB left to right and –74.81 dB right to left. The signal-to-noise ratio with an 8-ohm load from 10 Hz to 24 kHz with “A” weighting was –102.48 dBrA.
Strange how there is a huge difference between the crosstalk of the L/R channels. Usually the difference is like 1-5dB, not 11dB.
Here is the Yamaha 1020:
Two channels driven continuously into 8-ohm loads:
0.1% distortion at 113.5 watts
1% distortion at 129.2 watts
Five channels driven continuously into 8-ohm loads:
0.1% distortion at 63.9 watts
1% distortion at 73.2 watts
This graph shows that the RX-A1020’s left channel, from Audio1 input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 113.5 watts and 1 percent distortion at 129.2 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 146.1 watts and 1 percent distortion at 173.0 watts.
THD+N from the Audio1 input to the speaker output was less than 0.007 percent at 1 kHz when driving 2.83 volts into an 8-ohm load. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –103.60 dB left to right and –99.49 dB right to left. The signal-to-noise ratio with an 8-ohm load from 10 Hz to 24 kHz with “A” weighting was –107.17 dBrA.
From a purely preamp measurement point of view, the Yamaha looks the best. That crosstalk of -103.6dB is absolutely amazing. I don't know how Yamaha does that.
Here is the Denon 3312:
Two channels driven continuously into 8-ohm loads:
0.1% distortion at 122.9 watts
1% distortion at 143.3 watts
Five channels driven continuously into 8-ohm loads:
0.1% distortion at 82.9 watts
1% distortion at 103.0 watts
This graph shows that the AVR-3312CI’s left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 122.9 watts and 1 percent distortion at 143.3 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 202.0 watts and 1 percent distortion at 225.5 watts.
THD+N from the CD input to the speaker output was less than 0.005 percent at 1 kHz when driving 2.83 volts into an 8-ohm load. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –77.40 dB left to right and –77.93 dB right to left. The signal-to-noise ratio with an 8-ohm load from 10 Hz to 24 kHz with “A” weighting was –108.68 dBrA.
The Denon has the best power output here. Into 4 ohms, it could do 225wpc x 2ch.
Here is the Pioneer Elite VSX-52:
Five channels driven continuously into 8-ohm loads:
0.1% distortion at 88.5 watts
1% distortion at 109.2 watts
This graph shows that the VSX-52’s left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 108.7 watts and 1 percent distortion at 136.8 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 164.5 watts and 1 percent distortion at 211.2 watts.
THD+N from the CD input to the speaker output was less than 0.045 percent at 1 kilohertz when driving 2.83 volts into an 8-ohm load. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –91.98 decibels left to right and –97.12 dB right to left. The signal-to-noise ratio with an 8-ohm load from 10 hertz to 24 kHz with “A” weighting was –105.28 dBrA.
So perhaps the Pioneer Elite may just be the best overall performer.