I'm looking to run both my active speakers and headphone amp from my soundcards line out. Will this 3,5mm to 2x 3,5mm worsen the audio quality?

I'm starting to change my pc from gaming to multimedia pc (mostly music). Maybe i should sell my x-fi fatality soundcard and to get better sounding card? I was thinking of ESI Juli@. I dont have external DAC and i dont think im getting one anytime soon unless its better investment than new...

Atm i have cheap (2,5€ ) mini to RCA cable from my creative x-fi to Creek OBH-11 headphone amp. Is shorter better? 0,5m would be enough. Im not looking anything fancy just decent one im not sure how much they cost but i could pay up to 50€. Does better cables have much impact on sound quality?