Is not taking a second wife imitating the disbelievers or going against sunnah?

Does not taking a second wife (even after being able to treat wives fairly) fall under the category of imitating disbelievers? I heard that Abd ul aziz bin baz stated that in his book. Is it true? If a man is happy with one wife and doesn't want to take another (even after being financially stable to support second wife),then is he imitating disbelievers or going against sunnah?