Electronic – Amplifiers: IC selection and determining its correct values

I am onto learning and building electronics, and as a start I decided to build audio amplifiers. But of late the search for a good IC is becoming tough as there is an overwhelming amount of options.

So what is the general rule of thumb a pro follows when they do the search?

I also came across some resources, RaneNote – Audio Specifications and Understanding Amplifier Power Specifications from rayfes.com, that highlighted what needs to be the correct value any datasheet should show. If true, how to find out their values from the datasheet itself?

For eg, this IC MAX9709 does not specify the measured bandwidth of THD+N (if I am looking correctly). So how can I find out?

UPDATE
PS: i was searching for
– Class d
– Input power – 12V
– Bluetooth, USB
– Output power(RMS) – 80W
– Efficiency > 90%
– Total Harmonic Distortion(THD) <1%
– Signal to Noise Ratio(SNR) > 90dB
– Frequency Response – 3dB from 20Hz to 20kHz

So even after such considerations, there is surely some other factors a designers look for apart from cost. How do they make it easy for themselves.