Yeah, this is one area that I think Sonar is lacking in. I'm about to do a feature request on it, as a matter of fact.
You can do it, but it's not as easy as you describe it. First, you must chop your samples up in whatever way you can (manual or use Audiosnap), then use something like Session Drummer 3 to drag/drop your samples into that. You will only get the number of samples supported by Session Drummer at any one time, and not across the keyboard.
If your really serious about this, you can do like Bob mentions and consider something like Kontakt. And if you're going to do that, you should probably consider one of the Komplete packages. Right now's a good time because NI's having a sale on it.
Mike