need to do sound amplify from my pc without losing quality

I got Sennhessier hd 201 and creative SBS vx 5.1 sound card ... but sound is not enough for me.. actually average sound is coming.. i want little sound without quality and i have creative sbs a 200 speakers these speakers has no external headphone jack. Can i connect my headphone to Creative speakers with any type of cable. then tell me what is name of the cable....

or

please help me to increase volume in my headphones