I can't help you with the EAX settings 'cause I haven't owned a creative product in quite some time... but I can help with the speaker setup.
Based on what you said, the speakers have RCA inputs? Is that on just the subwooker unit? If YES, then just run one out to the subwooker/amp unit, it does the rest... if all the speakers have seperate connections, then that's what the manual is for
I have issues with manuals, you have to open them up and read them and thats just a little bit further than I'm willing to go
Actually, I got a GTXP that had no manual and there wasn't one on the CD included either. Hercules screwed up on some of the GTXPs in the transition from book manual to manual on the inluded CD. I went wrong when I missed the quick installation guide that came with my speakers. I just hecked the box and it says to get a 1/8 jack to RCA jack cable to set up the center/sub.
I had done this, but the center sound quality wasn't as good as the L/R and LS/RS. So I went back my Audigy for this and a few other reasons, that I listed in my Audigy Problamas Muchos post.
Also, I guess there aren't any settings for EAX with the GTXP. Its either on or off depending on the application.