We have four and are so used to it that it doesn't seem bad...to us anyway. I may be taking on a few more in the next couple of months as well.
Livi and Huck
might be expecting.
I think that the most difficult thing for you would be trying to get Nikki and a new puppy completely housebroken. Maybe once you have Nikki trained, it would be easier to decide on a 3rd.
Good luck on your decision!
Tammy