Your Woo WA2 puts out around 450mW at 70ohm. That is perfectly enough to drive the 2C loud. Audeze has recently changed their recommended driving power output for their headphones. It used to be 1-4W, now it is 250mW+. That means you get a loud enough experience above 250mW. Planars however regardless their impedance (and sensitivity) rating improve a lot with more power according to my (and other's) experience. Even the highly efficient HEXV2 improves with more power. The relatively low impedance of the 2C and LCDX for example can be deceiving. They do sound loud enough under 1W, but they really start to sing above 1W. Planars love current. If you are happy with the sound, don't worry too much. I am sure the WA2 does a decent job, much better than some folks experience here when they try to drive the 2C out of portable devices. However, the more power for planars the better. The sound tightens up, you gain more clarity and refinement. The most obvious improvement perhaps is improved bass control, tightness and clarity.