I would be happy with ripped 17.5s.
It shocking how "unhappy" you'll be when you get the 17.5s. To you, they look identical to the arms that have always hung at your side. You'll see them in the mirror and think, "when I hit the 18s, I am good-to-go". But you won't be, because even though the tape will be stretched to 18, you'll still see those 12" arms you flexed when you were 15. Then the 18.5s, the 19s.
It's an illness that we all have. I should know better, but I suffer too. Bigorexia.