If you are in NC, I would suggest you:
- do a 2x6 wall with advanced framing techniques -- 24" on center, two stud corners, ladder Ts, and insulated headers;
- celluloseblown in insulation; and
- 1" of rigid foam (DOW SIS) as the exterior sheathing.
The exterior foam will add R-Value as well as act as a thermal break. You can achieve an R-28 wall with this approach.
This wall assembly will perform as well as an ICF and will be approximately 20% the cost of the ICF wall.
For more information:
Read "What do you know about ICF construction? I am thinking about building a new home." a Q&A answered by William Janhonen.