SeventySeven - A few things to consider:
1) Budget - This will help determine what you should be looking at. You mentioned $3,000, but I'm not sure if this was the amount you were actually looking to spend.
2) It sounds like XC is what you are interested in. Providing this information to people at your LBS will help them direct you to some viable options.
3) Ride as many bikes as you can. If possible, don't just look at one LBS. As you are probably aware from road biking, geometry is an important factor in fit. There is some variability between different brands of mountain bikes, so the more you can ride, the easier it will be to narrow down what is comfortable for you.
4) Though I don't use Sidi Dominators, I do have a friend who has been happy with them. If you already use them with your road bike, it might be nice to not have to get a new pair of shoes for your mountain bike. Consider that they will likely get more beat up on the trails in the mud, water, etc., however.
5) As far as components, it sounds like you are pretty well versed already. If I were you, I'd ignore Zumba's post about Alvio and Acera.
6) In my experience on this forum, you'll get a lot of opposing opinions on forks. If you're looking at a $3,000 budget, you can probably be pretty comfortable that your fork will perform just fine. As you get more into mountain biking, you may look to upgrade to something more suitable to your riding style, but at the outset I wouldn't worry too much about it.