5.6 deg res is poor in my opinion. For $60, get the better res. But it also depends on the operating environment, like if you expect high interference, you aren't going to get good accuracy no matter what . . .
What would you consider high interference? I noticed that you have a Blade CX helicopter, I'm trying to use these in a Blade CX2. The gyro for yaw is right up near the motors, so is that safe to assume theres little noise coming from the motors?
Also, is there a gyro board that is accurate enough without amplification? The datasheet says the IDG300 (gyro on the 5dof imu) says it is rated for 500 degrees a second. Would switching to a lower degrees/sec (sparkfun sells 75 degrees/sec gyros) improve accuracy?
And going off on a tangent.. the 75 degrees/sec uses a ADXRS401 gyroscope. In RC helis the Futaba GY401 is one of the most popular gyroscopes out there, wonder if the GY401 uses the ADXRS401.