Again Creative, I know you follow this thread.
Please update the X7 to have an option for the RCA out (and perhaps spdif out as well). Something like a toggle button like:
RCA Line Out: Headphone amp mode, Speaker mode
and if possible:
SpDif out: Headphone mode, Standard mode
Once in Headphone mode, let it function EXACTLY like the headphone jack (volume aside, let it keep its speaker volume settings, since we'll be using an amp anyway, which more or less needs the X7...