Sound card or not to sound card

Hey guys/gals, Just put together a new system last night

mobo: Asus z77 v pro
case: Haf X Blue edition
cpu: i5 3570k 3.4 oc to 4.5
cooler: 212 evo
psu: corsair hx 750
ssd: samsung 830 128gb
hdd: Seagate 2tb
optical: Asus dvd rw
GPU: GTX 580

Now with this set up i mostly use myhead phones but i do have a semi decent logitech 5.1 and i have a SB audigy SE Sound care from my old computer that i havent brought over to the new build. My question is would it be worth it or is the onboard just as good?