I currently have 4 males and 2 females. I've had more luck with my males being more laid back and accepting to new furkids. Both of my females still growl and hiss at Alani and Blaze and they've been here for almost 1 year. I've found that females tend to be drama queens but I know there's always an acception. You're lucky that your current cat Butler sounds likes he's laid back and easy going because you certainly don't want to put 2 alpha cats together. I would also try to go by personality more than by sex. If it was me I'd get an orange male cat because for some reason they've always been very laid back, very loving, and goofy. I hope that the new kitty will help you find some comfort with your recent loss and will also help Butler too. Good luck.