It is generally easier to bond a male (neutered) with a female (spayed) rabbit. You definitely need to have the female spayed before you attempt bonding. Her hormones can bring aggression and territorial feelings which can lead to fighting. Rabbits can severely injure each other if they fight. You will also want to have her spayed to prevent uterine cancer. Unspayed rabbits have a very high chance of getting cancer. If you adopt from a rescue, the rabbit will almost already be spayed. That will save you money, worry about the surgery, and all the after care, plus you could start the bonding process sooner. You would need to let her settle into her new home for a week or two before you started bonding. A lot of shelters spay and neuter too, but some of them wait until the rabbit has been adopted, so you would have the recuperation wait in that case, plus the extra time for her  hormones to level off.

I’m not sure if your current rabbit would be upset at a new rabbit living right over him or not. If he considers that part of his territory, he might not care for it. If you did place a new rabbit there, you would have to make sure that they couldn’t physically reach each other or bite through the cage flooring.