$600 doesn't guarantee anything either. Some vets up the prices to deter people becasue the vet doesn't really want to do rabbits. A higher bill may mean better monitoring and medications, but doesn't necessarily mean a better vet. If the SPCA knows rabbits and neuters rabbits on a regular basis, it can be a good option. It is good to ask questions no matter where you go and not just assume that the price means everything.
How hormonal a male gets can vary. Some only hump a bit, others hump everything, spray, and are little terrors. Some are good around other rabbits, some aren't. You do sort of have to wait and see what he will be like. He could be fine and not really need to be neutered. He could also end up being a total brat that you want done as soon as you can.