With any luck (keeping my fingers crossed) I'll be buying my house within 90 days. I always said that whenever I got my own place I would get a big dog to be my watch dog (as if the yorkies don't fill that role enough...

)...but nevertheless, I still want a big guy (or girl) to stare out the window and scare people off...haha...and of course to be my big baby amongst all the little monkies.
There are certain breeds I really like...for example St. Bernards, Great Pyrenees, Huskies, and Shepherds...but I'm not sure how any of them would get along with the Yorkies and my cat. Somebody told me to stay away from the last two since I have the cat, because they really hate them...but others have said they can be fine if they're raised around them. Now I'm just torn.
I want a dog that will be a big baby to me and be gentle with the Yorkies, but at the same time will bark to alert me and big enough to keep somebody from breaking in if they saw him through the window.
Do you have any suggestions?