Kazuma
multiblitz, ive read on another forum that you plan to order many different SoCs from Odroid, BEaglebone and others.
There is an important issue you should be wary of.
For example, on yet another forum there is a long thread about BEaglebone.
And people quickly found out that i2s pins get burned very easily.
If you connect SoC i2s pins to a load, when load is ON, and SoC OFF, it fries i2s.
So, general rule is to use any galvanic isolator on pins (but sound gets worse usually), or strictly follow the rule to never power off SoC, while other device its connected to is ON
Just to give you a heads up, so your efforts will not be ruined with something simple as that.
Because you will need a lot of swaps while comparison tests, and better be safe.