Loud pop-click-pop from speakers every time I turn on/off computer?

[moeburn]

So I've got this efficient 150w amp, and these giant towering black monoliths that are KLH speakers; they're good enough for me!  But every time I turn on or off my computer, the speakers make a loud "pop-click-pop" noise, that's loud enough to scare my cats out of the room.  It is obviously the computer's sound card's fault, and not EMI being received by the amp, because it only happens when the speakers are actually plugged into the PC's sound card.
 
But they also make a (not as loud) popping noise every time I turn on/off my fan.  That is most likely EMI.  So I doubt there's any way to prevent my pc from sending that massive bass signal every time I turn on my PC (its an old Soundblaster Audigy card), but is there any way to filter it, somewhere along the wire or inside the amp, without affecting the quality of the sound that i do want to hear?  Because I assume if there is some way to filter it, it would also help to filter the loud noise I get from turning my fan on/off.
 
I should mention that all these devices are plugged into a nice Kensington EMI-filtering power bar, because someone suggested it might help the issue.  It did not.  I get the exact same popping noises and volumes whether I use the nice fancy EMI filtering power bar, or a super cheap surge protector.

 

[NA Blur]

You can read a bit about this here:
 
http://www.tomshardware.com/forum/350025-28-speakers-making-loud-pops-start-computer
 
Try turning down the volume to zero first both to and from the amp during PC power up.