personally i have never had any luck with imput monitoring. there has always been too much latency for me. If this is not a problem for you now, it may be when you try to fix your other problem. Basically, from what i have learned though personaly experience and great advice here, is that, by chaning the amount of buffers you use, you can either have low latency OR the ability to process many tracks and effects at once. I have never been able to have both. What sound card are you using again? If it is anything like mine (ASIO or WDM drivers in a tascam us122), you can go to the control panel and open your sound cards options window. IN there you can set the number of buffers your soundcard will use. This is Different than the options you have in the sonar window so don't get confused like i did!
Anywho, if you set the number of buffers to a low number, you will get a lower latency, this is better for imput monitoring because it is cloer to real time. If you set the number of buffers to a high number, you get a higher latency but your setup is more stable (i.e. no aduio droputs when you have lots of tracks and effects to process).
From all of that i guess my adivce would be to noodle with the amount of buffers you use to see if you can find a happy medium. If not, find another wayto montior your stuff. for example, i use direct monitoring on
my us122 which is dry but uses no cpu power. That way, latency is not an issue with me because it's already in real time.
If i have said anything wrong, anybody please feel free to correct me. in fact i would like to learn more about this myself.
good luck.