In my experience Fox Farm Ocean Forrest is by far the best soil that i have used. Its expensive as hell around my part (30 bucks a bag and a 3 hour total drive) but i will gladly dish that out everytime since i have real small grows. If you wanna keep it cheap you can always go with MG soil from Walmart. Be careful if you get that cause most if not all bags contain time release nutes which could burn up the little ones if your not careful.

Bobthis pretty much covered everything for ya. If your soil gets soupy you can always add perlite to your mix.

Wait a min i just caught something. Are you planning on using the 400mh for veg and cfls for flower? Or are you gonna do a total cfl grow?