From what I see on this board, your audio hardware compatibility with Sonar rests largely on your computer's hardware.
Motherboards, chipsets, CPU's and to a degree operating systems all have to work in harmony.
This might sound like a vague crock of bull, but if you scour this forum, you'll see stuff like "Hey, I use Sonar with this CPU, that motherboard and such-and-such audio interface on Windows 99 Super High-Test Release 17, and it sucks! How come?" Because one or more of these components is just not optimized for the others. There are people on this BBS that can explain the details, but it's not really important.
That being said, you did the right thing in asking about this here. The better question is "What is your computer/ audio hardware configuration?"
There are numerous that you can use and I would encourage people to post more than their interface. Give details on computer hardware and OS, too.
My setup is based on the system that Cakewalk uses to demo Sonar (at least at the Boston area Sonar clinics).
1ghz Intel PIII
256 mb PC133 ram
Abit BE6II Motherboard with Intel chipset
2 7200 rpm 40 GB HD's (one for apps/OS, one for audio data)
Windows 2000 with Service Pack 2
M-Audio Delta 1010
I'm able to record 10 tracks at a time at 16 bit 44.1khz with no probs. I've been playing back over 20 tracks, lots of plugins and very low latency if I want to do input monitoring. I could probably do the same 24 bit, but haven't tried it yet.
Good Luck