I'll start off by saying that I'm new to bicycles and the associated terminology, so to avoid having my eyes gloss over as I read responses, please keep that in mind.
I've been biking on my brother's $300 Giant MTB, and I'm ready to buy my own. I've primarily been riding on roads / compact dirt trails with gravel every so often. I'll be heading to a mountain trail today and see how that looks, and this will help me a bit in choosing the bike I want. The majority of the riding I'll be doing is still going to be roads and non-mountain trails, however if I eventually want to ride more mountain trails, I'd prefer not to have to buy a second bike or be limited by the one I buy.
My question is, I went yesterday to a few bike shops to look at bikes, and the brands available seem to be Specialized, Giant and Gary Fisher. My budget is $700, and I'm not going to go the 29er route. I do want front fork suspension, but my main question is one about tires. If I were to buy the GF Kaitai or Utopia, which seem to have 700C / 700x38 tires, would the frame / forks of either of these bikes allow for off road tires if I bought a second set?
What bike from these brands would you recommend?
Thanks for the help,