I removed asio4all from windows, and installed the latest MOTU drivers.  Here's what happens: it still defaults to WDM drivers.  When I try to set it to ASIO, it says my audio card (MOTO PCI 424) is unavailable.   In other words, it is acting as if MOTU doesn't provide ASIO, although on their site they say (if I remember correctly) it does. 
NOTE: I noticed the following: when I try to record a softsynth in real time, there is low latency until it glitches, and at that point it induces a large latency.  Don't know why.  I think it can handle it when I don't try to record simultaneously a bunch of tracks, which would imply drive overload(?).  I have two drives, I7, 16 gigs of ram, the performance meter is barely budging.  I don't have enough of a technical background to understand how this is happening. 

It has been quite a while since I did this - perhaps you need to de-select the input/output audio devices, in Preferences>Audio>Devices, and THEN go to Preferences>Audio>Playback and Recording and change the driver mode from WDM to ASIO.  THen click Apply, and if I recall correctly, then Sonar will automatically populate your input and output timing master settings to those of your audio interface.
 
I hope I recall the above properly, and apologies if not.  It has been a long number of years since I used WDM drivers.
 
Please try the above and post back, 
 
Bob Bone
 

Mr Bone, you are indeed God, as you were correct, that was the magic trick.  There was no way I could have guessed this on my own.  ASIO seems noisier,  but it may be that it has a higher output, and it is my preamps.  I'll run more tests on latency etc. and post back.

Thank you for the kind words - but I cannot take the credit for creating Heaven and Earth.  Glad you are up and running with it now.
 
I would suggest the following settings, for a starting point:
 
ASIO Buffer Size: 128
Sample Rate (both Sonar and interface must match on this): either 44.1 k or 48 k
Sonar Record Bit-Depth: 24-bit
 
I would suggest you shoot for at or just under around 10 milliseconds of total roundtrip latency, as reported in Sonar Preferences.
 
The above settings should give you a reasonable balance of it all, though you may have to increase your Record and Playback I/O Buffer sizes from the default of 256 up to 512 - but only worry about that if you still have trouble with the above settings.
 
Bob Bone
 

+1 Bob is a great guy!
 
Now that we have you in the best driver mode and running, take a look at these preference options and see where they are set (Edit->Preferences):
 
Audio->Devices: You should not be seeing a list of your ASIO devices, and to optimize your system, should only check the ones you are actually using (I typically leave mine as 2in/2out and leave the remainder unchecked).
 
Audio->Driver Settings:
Timing Masters: Be sure the two "Timing Masters" are assigned to your MOTU. This should happen automatically when switching to ASIO mode, but I have seen a couple instances where it did not.
 
The "ASIO Panel" button at the bottom is where you will want to set bit-depth, sampling rate, and ASIO latency. For my interface, I have found that it does run smoother when that panel is open while using SONAR, but this is not universal so is something else to check. I would start with something relatively "tame" and choose 24 bit, 44.1kHz sampling rate, and ASIO at 128. Verify that these correspond to the values on that Preferences tab (the only one you can probably adjust in ASIO mode is Sampling rate (the Audio Driver bit depth and Buffer Size slider will probably be greyed out). Note - some ASIO panels "lock" to SONAR, so you may need to do adjustments with this ASIO panel open, but SONAR closed, and then open SONAR and verify that the Audio->Driver Settings do match.
 
Sync and Caching (Advanced mode at the bottom): The I/O Buffer sizes near the bottom you will want to check and do this in tandem with the ASIO latency mentioned above (start with 512 for both of these)....
 
Increasing ASIO latency will reduce pops/crackles, but increase latency. Start at 128 for ASIO, and 512 for both I/O buffers. If you are still getting pops crackles, you may have to adjust to find the sweet spot:
 

1. Try adjusting I/O buffers (Advanced Mode: Preferences->Audio->Synch and Caching) both up and down until happy. 256 jumps should do.
2. If after trying all sizes up to 1024 you still have issues with playback, increase the ASIO latency to the next setting (Preferences->Audio->Driver Settings->ASIO Panel...) and go back to step 1 and repeat the I/O buffer adjustment.
3. Repeat as necessary until you find the "magic" combination for your setup.

 
Edit: Bob posted before me, I am glad our recommendations match!

Thanks.  The defaults that MOTU set are pretty much what you recommend, except 256 for playback and record buffers instead of 512, but it seems to be running fine.  If I run into trouble I can experiment.  Just out of curiousity, what is the relationship between the three buffer settings:mixing, playback and recording?
Geoff

The mixing latency is the audio buffer and is the round trip (digital delay) from your interface to SONAR and back out. This is important when you are using soft synth or monitoring from within SONAR itself (i.e. "real time" recording). Higher settings put less strain on your system, but increase the delay between your interface and SONAR (which can be noticeable if too high or using another mode other than ASIO). Ideally, you want to set this as low as possible without getting pops/crackles.
 
The I/O buffers (playback and recording) are buffers between your hard drive and SONAR. Too low a value may cause SONAR not to have data when it needs it and can cause drop-outs, too high a value can take too long to fill the buffer and also cause drop-outs.

@mettelus - I'm just glad I managed to match YOUR recommendations.  :)
 
I liked your explanation of the buffers, and concur on those, as well.
 
*edit to correct spelling*
 
Bob Bone