If you are building to a set of class rules that restrict cubic inch, then you have to have very good heads to compete. Only the best will do. If your goal is to just get to 2,000 hp with any size shortblock, the bigger the motor the easier and cheaper it is. The parts required still have to handle the power, but less boost/more cubes is a lot easier to work with than small cubes/huge boost numbers. The higher the boost pressure, the more the intake air temp goes up and the tougher it is to get it back to where you need it. I don't know about cost, but the turbos are the most efficient, prochargers close behind, then twin screw blowers, and at the bottom of the heap is the GMC style blower. A lot of it depends on what you like to work with. My personal favorite is a twin screw. Not the most efficient, but they have great power over the whole rpm range and no lag like some turbos will have.