Oh, man! I had a great reply typed up, and I got booted when I posted!
Let me try to summarize-
People hold fast to viewpoints and rarely budge, whether that's Christian vs. Agnostic or Mac vs. PC!

It's human nature.
The problem I see with religious thought is that most religious people do not view their own beliefs as living, breathing entities. Rather, they accept a certain doctrine at some point in their lives and hold on tight! What better way to truly believe something than to question it, contemplate it, and try to understand it on every level?
It sounds like your parents are absolutely sold on their beliefs, and this marriage aspect in particular, and that they're not going to examine other possibilities. Some people see this as faithful or devoted, and I won't tell them they're wrong, but I see it as a character flaw.
I'm sure that your parents are wonderful and loving in many other ways, but truly thinking about what makes their kid happy, and considering that it may not be the same thing as what would make them happy, is not one of those ways. It's true that they're looking out for your best interests in the long run, but that's totally under the pretense that you intend to live your life as a devoted Christian, which may not be the case!
Having said that, you ARE pretty young dude!
I'm not a whole lot older than you (unless you consider 24 to be ancient), but I can tell you from experience and observation that a 17-year-old's perspective doesn't always hold a lot of water to someone more middle-aged. There are many things for you to learn and discover about the world and yourself, so making a huge, life-changing decision can maybe wait. I think you should still see where it goes, but at least wait for a few years to seriously consider marriage. At least by then you'll be a bit older and wiser, and perhaps your interests and thoughts will stand up a bit more convincingly beside your parents'. You're still a kid (hell, I'M still a kid), so don't forget to enjoy that while you can! There's plenty of time to worry about serious issues like this!
