I don't have experience with 150W, but I would go for 1 or 2 plants using SCROG method. You need to control growth somehow (small space) anyway.
If you can, get blue light for veg (less height problems). Like MH or CFL.
Tip: feminized Indicas are great for small grows with space restrictions.
edit: rememeber, more plants does not mean more yield in your situation.