Dilemma - Asus Xonar Xense or Beyerdynamic DT 770 PRO

The problem is I will not buy hp amp very soon if I'll take DT 770 PRO and I need immediate results after purchase with very good sound for music production and monitoring (hard electronic styles with lot of low end: hardtrance, hardcore, etc; and orchestral music). Currently I have ESI Prodigy X-Fi NRG (Juli@ DAC), Microlab Solo 2 mk3 and ancient Koss UR-30. Kosses sound absolutely horrible with X-Fi NRG amp (and ESI saying its a high-quality one) - total lack of bass, too much highs, etc. While my ancient crappy speakers Genius SP-M16 driving these phones just excellent - good bass response, but with quite high noise. And I just don't get it - why ESI Prodigy X-Fi NRG amps driving them much worser, than some cheap shitty Genius speakers?

Anyway, if I'll buy Beyerdynamic DT 770 PRO, situation can be the same. Also, I'm not sure if I'll buy Asus Xonar Xense, there will be better amp, but if included PC-350 are tuned for this amp, so should be better than Beyerdynamic DT 770 PRO + X-Fi NRG or plugged trough Genius SP-M16.

What do you think guys, what's the better choice with current stuff I have - Xense package or Beyers? Thanks in advance.

DT 770 Pro 250 Ohm version. Budget is 300$. Not sure if any mid-end amp will fit in it and most importantly will drive them good enough.

 What about if to get Xense and stick with it and later get DT 770 Pro? Just DT 770 Pro costs here almost 300$ (cost and shipping). And Xonar STX, well, why I need Xonar or head amp without headphones anyway?

 Tube amps is a big no no to me. I don't need sound coloring, when I produce music - only clean fair output.