I tried connecting the audio output on iPad3 to line-in on my laptop, to line-in on the 5.1 Creative's speaker system, and to line-in on SB X-Fi (not all at once, of course ). In all cases, the music/sounds from the iPad were playing very silently, despite its volume was to the max (as a side note, the overlay volume notification when changing the iPad volume read "headphones"). The keyboard (and other system's) clicks weren't even heard.
If I connect various earpieces/headphones to that iPad's output, the sound is fine (and I can also hear system clicks normally). Is there some setting that can change the output, or is the impedance not right, and some preamp is needed to use iPad with external sound systems?