If you neuter your potential new male yorkie, you'll see a lot of advantages:
http://www.cuhumane.org/topics/neuter.html http://www.peteducation.com/article....&articleid=911 http://www.vospca.org/archive/spayneut.html http://www.kingcounty.gov/safety/Ani...Neutering.aspx
A lot of these should solve the past problems that you mentioned with males.
P.S. I'm getting a male too, and I'm definitely neutering him.
Good luck!!!