I have spent at least 15 years putting together my headphone system. I have used Woo amps for most of that time. If in a similar position I would invest in a Woo without hesitation. Also, one of my primary headphones is Focal Utopia.
Your kid is really lucky. I would have enjoyed a few bucks for tuition. The WA8 looks incredible, I would buy that for myself. Maybe I will. I use a A&K SP1000 DAP with my Focal Utopia, I am pretty sure the WA8 will blow away the amp on my DAP.
I think your son would be happy with either.