I know just what you mean, Cooper was 10 months old when I got Carley. I am all about the boys too, but something about Carley spoke to me. I was worried about how Cooper would do, he actually isn't a big fan of other dogs and he is SUCH a Momma's boy too.
They got along from day one and I know we were lucky there. I will always have two from now on, I think it was the best decision I ever made for Cooper and myself. He is still such a momma's boy and of course Carley is a Daddy's girl, and they really do get along really, really well. They miss each other when one or the other isn't around. I think if you have the time and the money for two, it is definitely what you should do. I found love isn't divided when you have two, but multiplied...just like with kids.
Best of luck with whatever you decide
also, I wanted to add, the first couple of days after I got Carley, I did question my decision, not because of Cooper, but myself, two seemed like ALOT more work at first, but after those first few days, when I saw how much he enjoyed her, she just fit right in like she had always been here..but the first few days, I did question myself.