worth a call or chat session with ASUS tech support to see if they will tell you who makes it; you are probably correct with Asetek, but I just spent about 15 minutes looking at pictures of that PC and doing a little research and could not find out.
It is a Maintenance Free cooling system.
I am and have been using a Corsair H50 for about 4 years now (originally built and designed by Asetek) with NO problems. Friend of mine has a similar system on his Alienware, no problems.
Hope this helps