3-4 psych/sociology courses will be plenty to adequately prepare oneself for the new section, just choose wisely.

The same goes for the modified biological sciences section. Yes, a biochemistry course will be very helpful for the new MCAT, but a major in it? Come on, that's overkill! A major in Biochemistry will have you jumping through all sorts of unnecessary hoops like calc II-III, physical chemistry, biochemistry lab, adv. chem lab, analytical chemistry, etc.

I would choose a single major that you love and include the following:
Core:
General Biol I/II
General Chem I/II
Organic Chem I/II
General Physics I/II
Biochemistry I
Genetics or Cell or Molecular
Physiology
Cell or Molecular or Micro or Immunology or Virology or Histology
Intro to Statistics
Calculus I or Statistics II
Intro to Sociology
Intro to Psychology
Choose 2-3:
Developmental Psychology
Biological Psychology or Neuroscience or Perception
Abnormal Psychology
Personality
Choose 1-2:
Bioethics
Dying/Death/Afterlife
Health Law/Politics
Medical Economics
Medical Anthropology
Infectious Disease
Epidemiology
These course will give you all the tools you need to nail the MCAT, and do will in medical school.