I have a question. Is he a collector or a shooter or both? Collectors often stick with a particular brand or type of bow. Shooters look for a bow that feels right to them. What bows does he have now? Do the risers (the grip part of the bow) look similar? If so, he may favor one grip (low wrist, medium or high wrist) over another. Again, if he is a collector, this might not matter. You could go with the unusual or hard to find bow for a collector or one that is particularly attractive to the eye. If you are looking for something he will be shooting and/or hunting with, you will need more information. The looks will be a lesser consideration, though still of some importance (no one wants an ugly bow).
We all have our opinions of the best bows, but if you look in the classified section you will see that bows change hands pretty regularly here. I have some that will stay with me (my Kanatis) and others that are nice, but I would part with them if something else caught my fancy. So don't get too caught up in what any of us recommend here. No one is trying to steer you astray, but we all have different tastes.
I applaud you for wanting to help your husband with his collection. The classified section here would be a good place to shop as most of the sellers here will do right by you (all have for me). If the bow is of good quality and condition, I don't think your hubby will be the least bit displeased! Find one you like the looks of and go from there.