TBH Lyr / Bifrost is overkill for the DT990, but if you want to future proof yourself that amp/dac combo will pretty much run almost everything else you may buy.
For DT990, I would go cheaper on the amp side and choose Valhalla 2 (if you don't plan on getting planars). Or, Asgard 2 if you do plan on getting planars.
Anybody start tube rolling with Val 2? Any cheap fixes for ~$50 or so, for either the 6n6p or 6n1p? I was looking at Foton gold grids for 6n6p, and maybe used Gold Lions or a JAN Phillips 6922 for the 6n1p.
I leave mine on for 10-12 hours + on the weekends since I have nothing else better to do, so I doubt it will burn the house down if you leave it on all day. It does run quite hot. But this is normal apparently for most Schiit amps.