SBX G6 would have very competent headphone amplifier for the price level, double so for Creative's B-stock price, and capable to driving most headphones.
(by Sennheiser's pricing it would cost like £500)
But if cheap phone&tablet level DAC/amp IC of GSX was enough for you headphones, then SB X4 would be certainly enough.
Also head shape customizable Super X-Fi HRTF would be advantage for gaming with possibly lot better sound directionality/positioning over usual fixed average head shape based HRTFs.
If you use speakers, HRTF options don't matter.