Hello,
I use x-cache on a couple of sites but not any WP. Normally I don't think it's a good idea to use x-cache for cached files, I would just use the W3TC enhanced disk storage method and let Apache just serve them out directly, no php involved. That option might be disabled because x-cache would not store them anyway because there is no php.
Just let x-cache process the WP php files because that's what it's good at, W3TC would have nothing to do with that.
When you look at your XCache x.x.x Administration page and select the list files do you see all of your WP php files listed? The beauty of x-cache is how much the file size is reduced in memory, for example the file at the top of my listing is 82k but the srcSize is only 9.5K and it's being served directly from memory so it's quite fast.
Craig
