dillyboy
Can any keyboard that has midi ins and outs be used for X2, or is there any more advantage in using a Roland or Cakewalk keyboard controller.
As just a keyboard (I mean to play notes) all of them are equal from Sonar point of view. But as a controller, functionality can be different. Roland/Cakewalk controllers will work out of the box, with wide functionality coverage (see help files for corresponding Control Surface plug-ins). Other controllers with special Sonar support (like Nektar Impact) will also work out of the box. Any other device without Mackie Control emulation you are going to configure yourself using standard Sonar plug-ins (not a big job, see chapter 40 in the Sonar Reference Guide). But do not expect any feedback (like LEDs under transport buttons or rings around endless encoders).
And with any controller you can use my plug-in, but till you get the device for which some preset already exists, be prepared to spend quite some time, especially in case you want fancy results (like indication of track volume/meter using multicolor pads).
For practical mixing, it is better to use separate controller with proved Sonar integration (V-700, MCU, Faderport, Alphatrack, BCR2000, depending on money you can spend and the functionality you need, for example MCU is a bad choice for VSTi control).