[HerrXRDS]

I recently upgraded my old, low impedance cans to DT990 250Ohms, I was not expecting this to be so complicated. I've been reading this forum for the past two days, developed a serious headache and things are still unclear so if you could give me some advice I would appreciate it.  
 
Currently I have an on-board ACL1150 sound card, I've ordered the DT990 and a SoundBlaster Z to drive them. Soon after. I've read that the SB Z is not enough to drive them despite it's advertised 600 OHM amplified headphone port, so I've ordered the Schiit Magni 2. Now I've found about the problems double amplification can cause

.
I am using this setup for games so I need to use either the amplified headphone port or SPDIF if I want to keep the surround effects.
If I get a DAC like D03k to use on SPDIF, will I notice a big difference compared to using the headphone port? Do I need a more expensive DAC to be worthwhile? 
 
As you can tell, my standards are pretty low, I just want something that sounds nice and this is getting a lot more expensive than I was expecting, so, is this configuration decent:
Sound Blaster Z > Magni 2 > DT990 ? 
Should I go with: 
Sound Blaster Z > D03K > Magni 2 > DT990 ?
Or maybe ditch everything and use
ACL1150> AudioEngine D1 > DT990
or
ACL1150> SMSL SD793-II > DT990

 

[HerrXRDS]

After reading a few more threads about similar setups, it seems like a SBZ> SPDIF DAC > Magni setup won't make a difference compared to Magni connected directly to the amplified headphone port on SBZ. Apparently double amping isn't that bad and the DAC on SBZ is good enough. I think I've reach a threshold of diminishing returns for my money.

 

[PurpleAngel]

I found the SB-Z fairly decent at driving the 250-Ohm Beyer headphones.
 
But I guess you can try connecting the Magni 2 to the SB-Z's headphone output.
 
If all your doing is listening to music, then plug the Magni 2 into the front speaker jack on the SB-Z and set the SB-Z for 2-channel speaker output, should give you the best possible music audio quality for the given hardware.