What are you planning to cool btw?
If you want silence with low rpm fans and still have low temps then bigger rad is the answer.
I used prior to my AMS 840 a alphacool 360 Monsta rad and a xspc rc480 rad and my AMS 840 trumps them both temps wise. Sure the AMS 840 is bigger but I have no regrets and others who use it don't either. There are some conflicting reviews about the AMS rads one says it's mediocore while others tell it's really good. Real world application with my AMS 480 on my fx-9590 is at 100% load 51c, idle is 27c. My previous rad was a xspc rc480 idle was around 31c - 33c at same room temp.
As some one mentioned add another (cheaper) rad to your existing setup that should do the trick as well. There are many good rads for around 90 bucks or cheaper. And save the money for something else for your wc or pc.