I have 3 dogs... and while I love them all dearly... I will never have 3 again! I had a 10 year old Dalmatian and a 9 year old lab and got a little Shorkie. He was 2 pounds and my dalmatian worshiped him.... my lab hated him. She growled at him whenever he came near. After about 6 months I was seriously thinking that I was going to have to give my little guy away, as he caused my lab so much stress. (She's older, plus diabetic, allergies, ACL...) Then out of the blue one night my pup tried yet again to get her affection and low and behold my lab started to mouth wrestle with him! Boy was he so happy! They played for about 10 minutes. Since then they've been great! That being said... 3 is still too many for me. Even though I put my 2 girls on a coupler with 1 leash, and little guy on his own leash it's still not an easy walk. I used to take my girls with me places, even softball games. But now with 3... that's just too many to tie up and worry about while I'm on the field. So now I just take my little guy so we can play fetch in between innings and my old girls stay home... Plus... the added expenses! He's only 10 pounds now so food really isn't a huge factor... but his PET INSURANCE sure is! That's another $55 a month... and then vet bills. Thankfully he's been pretty healthy but the stuff he has had done $$$
And... now you have another dog to give love and affection to, which in a way takes from the original pups.
So... I think that I will always have 2 dogs, so that they keep each other company, but I will never have 3 again. Good luck with your decision!