A 250 ohm DT 990 will need a headphone amp while a HD 598 won't. The 598s are more of a neutral presentation while the DT 990 is a heavy V shape with emphasized highs and lows. Some people find the treble of the 990s to be almost painfully bright. For only gaming the DT 990 is probably more 'exciting'. I haven't heard the 990s but I own HD 598s and still use them for gaming despite having better headphones for music. The 598 is light, very comfortable and has great soundstage.