I ran FSX with the AXIS assigned to the Toe Brake and FSX indicated "Differential Brakes".
That's what you should see. With your toe brake axes properly assigned to both left and right axes, you now have left and right independent 'proportional brakes' (the harder you push, the greater the brake pressure unlike the brake key/button which is all or nothing).
If you apply 1 or the other (or both, but with different pressure), you'll see 'differential brakes', and the aircraft will pull in the direction of the greater pressure. If you apply both brakes with equal pressure, the message will change to 'brakes' (indicating equal pressure) and should provide straight slowing/stopping.
To my knowledge (not being a rw pilot) this is the way it works in those ac that have the rudder/toe brake pedals.
As for the Cirrus drivers, if you're having problems it might be best to go to the PFC-
http://www.flypfc.com/-site and look or ask in their support forum (registration required to view forum).
Once you have the toe brake axes assigned, you should run 'calibrate..' in the 'Calibration' tab. After calibration, if you are seeing the 'differential brakes' message when you are not pushing either pedal, the sim may be reading one of the axes in the wrong direction. You may have to put or remove a check mark in the 'reverse' box for one of the axes in the 'control axes' tab.