kimikaw, if you would really feel more comfortable with wider tires, you could also consider a cyclocross bike. They work perfectly well on the road, often have sturdier tubing than road bikes, and can fit tires up to 32. I've got a Specialized Tri-Cross that's been adjusted to have a touring-type fit and it makes for a very comfortable, sturdy road ride.

And Oakleaf's right. Bicycling Magazine frequently runs articles about folks weighing 300+ pounds getting into cycling. You're a feather compared to that, so definitely don't worry about your weight. I would think that the two most important things to consider are the type of riding you plan to do and whether the bike's geometry can be adjusted for your comfort.