I admit I have not, but I have a couple of friends that have which I suggested them the DT990 pro-250 and they love them. One of them uses them with a sound blaster Z, which make them sound very good to him. He had them plugged into a Xonar DG, but he didn't like how the DG performed with them. When he went to the Z it made him smile. He came from a pair of AD700's which he liked the DT990 pro-250 more then. Open back headphones tend to have very good sound imaging. He does find the DT990 pro-250 plugged into his Z more detailed then what he used to but he enjoy it alot. results can change based on the source that is used and or source and headphone amp.
Your motherboard sound is still onboard audio, it just not attached to the motherboard but is on a card. It still will be a weak link in the chain and wont do the DT990 pro-250 justice any way or any headphones for that matter. a sound blaster Z which will o them more of a justice then your onboard. But most important, I should had asked you which sound signature are your looking for, but I didn't.
I have used Audio-Techinca AD700, Ultrasone HFI-780, AKG 702, Beyerdynamic DT880 pro-250, A900X and DT880 premium 600 in that order with games and out of that order the ones I liked the more besides the Current Beyerdynamic T90 that I use for every thing, is the AKG 702 and the A900X The AKG k702 very wide sound stage was the main reason I liked using Dolby headphone with them they being too analytical in the high and mids ruined them for me as well not having a little bit more bass, While the A900X I liked a lot, but I miss the sound imaging and the open back headphone sound stage.
Edited by genclaymore - 6/17/14 at 7:41am