If you just want a desktop based combo, one good option would be to use the FiiO E10 as USB DAC for the E9. This is the setup I'm using right now, with a FiiO L2 cable to connect the E10 and the E9, and I think this setup is far superior to the E7+E9 I was using previously in every way. Price wise, an E10 or an E7 should cost around the same... 
Regarding the DT 990 PRO, which I also own, adding this combo will give you more volume and detail/resolution from your music, but in terms of bass, I think you should start looking at other headphones. Those Beyer's are great, but they will never be basshead can's, regardless of the Amp/DAC you use! 
Quote:
Originally Posted by
ineedmorebase 
thanks, was just curious to see what the diffrence would be on my dt 990pros with either the e9 or e7/e9 combo, i want more BASS powaaa since im a basshead and they are semi-open...thanks!
also, should a get a soundcard? or does the e9 take care of all that a sound card does?
thanks!