I can't help you on the mixed breeds but I do know there are others who post here who either have one or know someone who does so they may be able to provide some information on that.
As for getting another one, I say go for it as long as you can make the commitment to 2 furbabies instead of 1. Both will need love, attention, discipline, and nurturing and you can do it! I can understand your concerns about being able to love and care as much for the other as you do for the first but....God ALWAYS provides enough love in our hearts to go around
I felt the same way after my firstborn son - didn't want another because I didn't feel I could love another child the way I loved him. Boy was I wrong. I have 2 sons and love them both equally and unconditionally. And I have 2 yorkies who I treat the same, love the same, and who both of them love me. One is a joy to have in the house, 2 provides you double the fun, double the laughs, and yes, double the love!!!
Best of luck to you
Suzi