I would still stick with the 158 if I were you. If you're an early/intermediate rider, you may still get in the parks. A lot of people go into boarding with the idea they're going to stick with only one type of riding, then 2 years later they're doing the exact opposite. You say you'll never hit the park, but in a couple of years of riding you may figure out you actually enjoy it.
The 158 will allow you to still hit all types of riding while you're learning and figuring out what you like. In a couple years, when you've figured out exactly what you want to do, you can pick up a more specialized board that is better at what you like anyway.