Some background quickly. I'm on a racing team sponsored by Specialized that primarily does mountain bike races, but I'm a roadie. I hadn't touched a mountain bike for years and had never raced one before yesterday. I own an old heavy Trek hardtail, but borrowed a teammate's Gary Fisher Sugar for the race, and had a fun time, and did much better than I thought I would. Now I think I want to get more into mountain biking, and I'm at the bottom of the learning curve. All the component levels, etc. are foreign to me.

I'll get a Specialized, that's pretty much a foregone conclusion. I'm almost certain I want an Epic, from everything I've learned so far they seem to be the best fit for the XC racing around here, and that's what many teammates have and are recommending. So, my main question is really about the differences between the models. Do they get much lighter as they go up the line? Do the carbon frames have a better feel than the aluminium ones? The expert carbon is about the same price as the alu marathon, so is going to the carbon frame a reasonable tradeoff for the lower components, or would I be better off with the higher components? Is the frame the same on the marathon carbon and expert carbon, and it's just the components that are different?

As a roadie, I tend to be a weight weenie, and spent a lot of time, energy and money optimizing the weight of my Tarmac to be under 14 pounds. I have a feeling I'll end up doing the same within reason with the Epic, so I figure I should start out with a reasonable component mix, but if there is anything in particular I can replace to shave weight, would I be better starting with a frameset or a lower component mix?

Sorry, lots of questions, just trying to get up to speed on this crazy mountain biking stuff.