Found this, wonder if comparable to the X5's
http://www.e90post.com/forums/attach...2&d=1266451970
Specs for systems above.
Hi Fi system speakers are all 2 ohms

I wouldn't assume the numbers are RMS since marketing likes to brag about power output and furthermore they are into
2 ohm speakers in most cases .
Worst case its peak power and if you used 4 ohm speakers which are accepted
as a standard value these days it would be half the stated values for power.

So assuming you use there numbers and assume peak power in 2 ohm speakers You have 40 for the underseats and 25 for the doors .(Hi Fi system)
Divide by half for a 4 ohm rating which is 12.5 and 20 mulitply .636 for RMS
and you get 6.36 watt rms and 12.7 RMS depressing isn't it.