By all means use ASIO, but there is no technical reason why WDM/KS should have a higher latency and in Sonar, KS has an advantage if the very lowest driver buffer won't work but the next step up is too high.
The very lowest soundcard DMA buffer is usually 64 samples - how low does the MOTU go?
Try this - set the MOTU DMA buffer to minimum, open Sonar and (using WDM/KS) make sure the latency slider is at minimum, buffers in playback queue is 2.
Run the soundcard profiler. You will then see the lowest latency your system is (theoretically) capable of. You can now fine tune the performance by raising the latency slider a notch at a time until you have glitch free recording. If the MOTU buffer was 64 samples (about 1.5 to 2ms at 44.1 or 48Khz), then the slider will allow you to adjust in increments of whatever the minimum was.
Note that driver setup panels and Sonar often report different latency times for the buffer value - some programs round the figure up and some round it down, and it will be less the higher the sample rate you record in. If you always want to record at 88.2 or 96Khz, a buffer of 64 is a bit impractical, 96 or 128 is probably better in that case. If you are running plugins using input monitoring, the latency you hear is at least twice the figure you have reported to you - it has to go in and then back out + the plug-ins own process buffer + the hardware buffers on the interfaces convertors. 11.6ms is actually a little over 25ms in practice for input monitoring. That's equivalent to playing a guitar while being 25 feet away from your amp - hence your timing difficulty!
If you use ASIO, you will only have the choice of latency provided by the MOTU buffer size selection.
Have to say though that I've seen very uncomplimentary things about MOTU Windows drivers - they have a better reputation working on Apple systems. Might well be worth checking if there is an updated driver on the MOTU website.
I'm assuming you have your pc hardware and Windows o/s are optimised? These pro interfaces need a clean machine - you can't often get away with a default Windows install as you can with a normal Windows soundcard system, not if you want the lowest latency pro interfaces can provide.
