Perhaps it would be beneficial for you to visit the many threads here that are dedicated to Schiit Audio's magnificent gear.
I am the owner of several of Schiit's marvelous products and I can readily remark that, where FiiO is what I would consider "Middle of the Road" audio production adequacy,(I too have that FiiO 9, I use it for very casual listening with a set of closed-back cans during the summer when there's a fan running and I care rather less about superb sound quality than something that amplifies well enough to block the fan noise for me to doze off...), a kind of "general public" amplifier,...Schiit products are in a different class of build and sound quality. They are capable of elevating one's listening experience to excellence, instead of being kind of average, or "well that's good enough, better than without an amp..."
FiiO get's you there, Schiit takes you BEYOND, or DEEPER.
I guess the fact that I own a FiiO, yet still decided to purchase multiple Schiit products may be the best recommendation that I can offer you about buying the Asgard2.
The Schiit will exemplify your 'phones in a way that the FiiO can't, PERIOD.
And, remember, FiiO is, essentially, mass production. That's not really an advert for build quality, IMHO.
This sounds kind of snobby... but I won't even let my nicer cans,(Audeze, Senns, higher end Beyerdynamics), LOOK at the FiiO.
Not that is can't make things louder....., it's just not good enough.
Getting Nice Headphones can only take you so far if you don't have he noise making gear to take those nice 'phones to their potential.
I'd really do it, if it were me, and I knew that Asgard2 is fully functioning, and all I had right now is a FiiO.