I recently purchased a Nektar Impact LX61 which was the only keyboard controller short of the A500/800 that advertizes Sonar integration. The stock mapping is fairly good with control of the transport and mixer (w/ WAI bank switching.) It should be possible to use one of the "user programs" to map the ProChannel to the surface, so I am reasonably satisfied with this setup, although there are some glitches with the controller's ability to navigate through the synth rack. While I appreciate Nektar's providing Sonar support, their flagship Panorama line does not integrate with Sonar.
Prior to the Impact Keyboard, I purchased (and returned) a QCON Pro which is a Mackie Control knockoff. It did not work well with sonar but it did work well with Samplitude. However it is my observation that it is relatively difficult/impossible to intelligently map a MCU to instruments and FX, even if the DAW provides this capability. I believe the Mackie Control is "dead" technology. It gives you flying faders, but the faders, bank switching, arm/solo/mute is about the only part of it that works well.
I also investigated the Novation SL61 Mkii which touts Sonar integration. This may be the best option for control of sonar plugins, but there has been alot of Automap "hate" reviews. I'm not sure how much better it is than using ACT, although it does give you a visual of some controller parameters. However, this is a five year old controller, and I'm not sure I want to get on board with legacy technology that gives many people fits. The newer Novation "In Control" protocol does not integrate with SONAR.
So the current situation with regards to control surface integration with Sonar looks bleak. The Impact LX61 and A500 are budget controllers with only partial integration. The Mackie Control is legacy technology that does not have a strong Sonar plugin. The new generation of integrated controllers (Nektar, Novation) are not compatible with Sonar.
What does Cakewalk need to do in order to gain compatibility with the current generation of hardware controllers? It seems to me that the onus for this is on Cakewalk; the hardware makers would advertize compatibility if it was possible. I know that Sonar is the only DAW to provide multi-touch capability, but prior to my control surface journey I tried touch with Sonar and touch does not rival what can be done with even a simple surface. I think the ultimate problem with touch is that the finger blocks the parameter being adjusted and unless every plugin UI is develped for touch, it will be more hassle than its worth.