the dt990pro is an excellent pair of cans for the money, howver at 250ohms you will need either an amp or decent soundcard to drive them. they are open, with fun profile, decent bass and crisp highs. i would say they are better than the 558/700 for anyone who likes a bit more bass.
if you did not want to get a soundcard or portable amp then you want either the hd558 or ad700x. if you like a bit more bass, go with the 558. if you dont care about bass at all then go with the ad700x.
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for the record... the dt990pro can be paired up with a $30 xonar dg if you just needed them amped or the $80 creative z which would give you better quality than onboard and also allow them to be amped.
if its in budget... this might be the better set of cans for you however with soundcard you will certainly exceed your budget.