"Well...I have a bracket that came with my motherboard...it has SPDIF and a Coaxial outputs....can i use any one of these...if i'll use it..i'll have to diable the soundblaster card and activate the ONBOARD audio.."

No you won't. If you're into gaming you may keep some of the Creative enhancements you may lose by using motherboard audio. The SBLive! series all had a digital out option of some sort. On the first ones, there was a separate bracket with both Optical and Coaxial in/out. According to the Creative site this is still available. On later models, the Digital out was either the topmost jack on the card, or on some versions it is also on the Green jack. You select "Digital Output Only" in the Creative mixer app. (or in the windows mixer by selecting advanced settings below the master volume) to change from Analog to Digital out.

However, your receiver will only decode Dolby Digital games, not EAX four point surround. For non DD multichannel games with four point surround you'll need to let the card do it's thing by using three 3.5mm to RCA adaptors in the green, yellow, and black jacks and plugging these into the 6-channel direct in on your receiver, assuming your receiver has one. Green is front l/r, black is rear l/r and yellow is center/sub.