bloodhound,
Check the pedals for the clicking, see if the sound happens under load or all the time. My son is 6'4" around 280#. He has a Haro MTB and had a noise in the drive line that no one else could find. It has bugged him for almost a year, I finally rode the bike the other day and "felt" the noise in the pedal, replaced them and no more clicking. I am not familar with the Sirrus, but pedals seem to be a place where a lot of manufacturers drop the ball and use something cheap. But pedals are realtively inexpensive to swap out. And many people do, usually for a clipless.

Aaron