I know that sirius is a double star and I have tried to split it a number of times with my 4.5" reflector, with no luck every time.
Toninght I decided to take out my trusty digital camera (fujifilm S5500, 4mp) and pointed it at sirius and took a picture. I couldn't see anything after I took the pic and then decided to zoom in on it, and sure enough there are 2 stars next to each other, one is a little smaller then the other.
I will post a pic as soon as I figure out how.
I've had no problems splitting this puppy in both my reflectors at powers of only around 100x. Good seeing is the key, as bad conditions will really distort Sirius, cause massive flaring and quivering and completely wash out the pup.