I dunno why you brought up Wi-Fi?
Going to XLR changes nothing wrt "quality" of output unless you're getting RF interference or going ling distances.
Spending more on a bigger DAC is throwing money away, especially if all you want is a higher voltage line driver.
Which it turns out you don't even need, since you have no real problem?
Assuming the answers to these
> Are you now saying that your only problem here is the SCALING if the volume control? Like you need to turn it farther "up" to get to the max SPL you want?
and this
> Are you reaching an SPL higher than you actually want to play your system?
are YES.
We're spending hours here collectively advising you, least you can do is answer direct questions!
> That is not a problem, in fact it's A Good Thing, gives you finer control.