You need a foundation design prepared by a local professional, with expertise and liability insurance, so that if there are any problems you will have recourse. You are talking about a 2400 square foot house footprint, which is a pretty good size. Your local professional will understand what works in your area, what building code requires, and what should work best on your site. Local contractors may have someone they work with in the area to design the foundation, in my experience the contractor often does not design the foundation, they have an engineer or architect they work with do the design.