Coupling Capacitor upgrade? Which one first?

Amplifier input cap isn't related to cutoff frequency in this chip amp. (cutoff frequency determined with feedback cap and feedback resistor value wrt to datasheet).
I begin to guess amplifier input cap is much important than dac output caps(if amp doesn't have input cap, then dac output cap becomes have same level importance).
Just I wanted learn you/someone have similar conclusion..


I also don't understand why manufacturers don't have any info about their capacitors. 
I don't expect too much thing from a capacitor. Enough clarity with vocals, good soundtage stage info, good bass, neutral, coherent, neutral tone.. 
Basically it should be transparent(in my perspective it is The same thing with clarity).
I don't know what these words mean in science.. 

Amplifier input cap isn’t related to cutoff frequency in this chip amp.

It will relate to the low frequency cutoff with input impedance of the amp.
If the amp is 47kohm input and the cap is 4.7uf then the bass rolloff is -3db at .7hz (a good figure)
If the amp is 1kohm then it’s -3db at 33hz (not good, bass light) and I’ve seen some chips amps with 1-2k input impedance

Cheers George

Input impedance is 30kohm wrt datasheet. 

.9hz -3db with the 4.7uf cap fine, just bridge out the dac cap.

Cheers George

I didn't like the scratchy noise while I moving volume pot when I removed the dac output caps. I am planning buy an headphone amp which have not input caps. This can be problem.