At stock speeds and decent case cooling, I think it would work.
I built a system for a friend of mine with hearing problems consisting of a X2 4200+ running at stock speeds and the Ninja without a fan. The load temperatures maxed out around 58-59C while dualing priming, and while just a little high, the system was perfectly stable. This was in a P150 case with a 92mm intake fan, a 120mm low speed exhaust, and the 120mm fan in the PSU.
The Scythe fan is extremely quiet, and in the end, we installed it on the Ninja.