If he is really all that
Then he will be extremely respectful of your marriage. In situations like yours the relationship between your husband and your boyfriend is extremely important. Please remember if he is really all that, your boyfriend will understand why he also needs to be concerned about how your husband is dealing with it.
Frankly, without that concern, and in the very least, a whole lot of respect, it is drastically more likely that these relationships will come with a lot of completely unnecessary emotional pain.
It's is great that you get along so well, but remembering to love responsibly may make your life much easier for all involved. I you are not practiced with honestly knowing the origins of all of your emotions, I would be worried able unconsciously setting yourself up for problems.
But if you all are genuinely concerned about each others emotional health, it could also go smoother than one would think possible.