I suggest you try installing the zebulon packages, his version of sabnzbd is up to date, the mertymade seem pretty old.
If you add the zebulon repository as an external source in package manager, I don't think those versions check for architecture, so that's one way around that problem.
To manually edit the package to enable cedarview here's a step by step. You need the program 7zip to do this.
Download the spk file, for instance SABnzbd-x86-0.6.15-2.spk and then rename it to SABnzbd-x86-0.6.15-2.tar
Use 7zip to extract it to a folder. Inside the folder will be some files including one called INFO. open up INFO in wordpad and change the line that says arch="x86" and change it to arch="x86 cedarview" then save the file.
Highlight all the files in the SABnzbd-x86-0.6.15-2 folder and right click and choose 7zip - add to archive. 7zip will pop up. Change the archive format from 7zip to tar and it will create this file SABnzbd-x86-0.6.15-2.tar
Rename SABnzbd-x86-0.6.15-2.tar to SABnzbd-x86-0.6.15-2.spk and you can use that to install it. But again, I *think* if you go to package center, other sources, and add this url http://synopkg.superzebulon.org/spkrepo/packages
the packages will show up in package center and those versions don't check for what cpu your nas has so they'll just install.