#Sound Blaster Z would drive 250 ohm Beyers fine.
While needing slightly more voltage, DT990 draws lot less current and is hence less power hungry than AKGs.
Again it might struggle in driving AKGs in some circumstances, if you don't care about hearing safe sound pressure.
AE-5 and G6 again can certainly drive those without problems.
AE-5 can even push out more power than AKG specs those headphones to survive. (200mW)
But actually there's possible development coming in sound cards:
We hear in 3D with two ears, because head causes direction dependant changes to signal received by both ears from sound source.
Unfortunately that "upstair's guy" forgot to standardize human head shape.
So if listener's head shape isn't close to average, immersion can suffer because binaural cues aren't accurate.
Creative has developed and finalized tech with head and ear shape customizable HRTF algorithm.
But so far it's available only in audiophile priced USB dongle for phones/tablets without sound card's normal features, or even PC based control software.
So might be that Creative is readying some new sound cards to replace Z-serie.
I know i'm probably asking some really silly questions so apologies. But is the AE-5 better than fiio e10k?