LawTunes
I hope this is not a dumb question, but is there another DAW than can directly and effectively open or import Sonar project files, with project settings, etc. intact? I assume none will be perfect, but that could reduce the labor a bit.
Not a dumb question, as that there would certainly solve the whole problem!
But as it stands today, the answer would be no.
Each DAW is developed with proprietary song/project file formats, that record the settings of various project features present that will not necessarily correspond with features in another DAW. There are no universal standards for projects, just the raw audio and MIDI file formats.
So cross-DAW translation would be a very convoluted task to undertake, and would require a lot of investment to hit a moving target, as each DAW out there continues to evolve and change. It's a task for manual labor.
The only practical plan is to export all of your audio and midi tracks from your project as files, and then import them into your DAW of choice, where you will need to re-create the project in the new DAW.
You will lose all of your original projects settings, such as mixer settings, automation, busses, FX, instruments, etc. Also probably a good idea to save the instrument and effect plugin presets used with names relating to the specific project. So you will probably want to have the two running side by side for comparison.