I certainly don't want to dissuade anyone from using Linux as a DAW. I love the fact that Ubuntu has become somewhat of a standard Linux, and it can run some serious applications now. I still find it more clumsy than Windows, but nobody can argue it's rock-solid platform and lower harddrive consumption. It's quite efficient!
But I personally would not try using Linux to emulate a DAW, regardless of how fast the emulation can run. Unless the DAW is tested and supported for that hardware, I would highly recommend against doing it to save some $$. Just ask anyone who's tried running MAC OS X on a PC, and you'll find very few of them successful, and even less than that number recommending MAC OS X running on a PC.
Sure, there's some success, but only in a perfect environment of hardware, drivers, and a little bit of luck, but I dare say that absolutely none of them said it performs faster than a real Mac, and that they didn't encounter some strange errors along the way.
With all of that said, emulating Sonar on a Linux machine in at least some stable method might be useful for editing or automating, things you may not need super speed to accomplish. I have a Mac Book Pro from 2012, right before the retina screens were released. From what I've seen, it performs well for DAW work, but it's a total dog for other applications, such as Camtasia, Photoshop, Mac Mail, and even this forum. It's a slow performer when it comes to multi-tasking. I won't consider using it for DAW work at all. As a VM, Sonar performs very poorly on this machine (I tried it here to test editing).