First of all, thanks for the help on a recent query.  I found a 10 second wav file of an ambient bed sound that I'd like the middle 6 seconds or so looped.  While I know i can just copy and paste the file and then use crossfades to essentially loop it, I suspect there must be some sort of sampling VST in Sonar that makes this simple.  I tried opening a simple lead sound in Rapture and then loading the wav file as the sample (overriding the triangle wav that the preset originally used), but it definitely changed the sound too much, and it didn't loop.  Can anyone give me some pointers on how I could most easily do this?  Running the 08/17 version of Splat.  Thanks in advance!

Yes, you can drop a wav file into a cell in the Groove Matrix, or drag it from the timeline, and it will loop over and over. 
 
Matrix View works a little bit like Ableton's Session View.
 
You can also select just a section of a wav in the track view and Ctrl-drag/copy only the selection into a cell, without cutting it first.  You will need to enable "Groove-Clip Looping" (Ctrl-L) for the selected clip in track view if you just want a selected part of the clip to copy, else you will be bringing the entire clip into Groove Matrix, not just the selected part of it.
 
So that works if you just need to loop few seconds of a 10 second clip.

Select the clip-> open the inspector->select clip at the top of the inspector-> select groove clip-> check the box for looping-> Drag the right side of the clip for the desired length.
 
Rocky