Hi there ganja lovers. I am in the design process of my growbox, I have read forums posts, watch videos, and did a lot of research before coming to the following conclusion for my setup. However since this is my first time I will love to get some feedback before I put everything together. My idea is to have 1 to 2 plants most likely Northern Lights, since I read that they are a good starting plants for a beginner.

I have decided to build a 2x2 box and making it 5 feet tall. Paint the inside of the walls white so it reflects the light back, Use a 120mm pc case fan which is rated at 110CFM at the top of the case for ventilation, while having an air intake hole somewhere on the bottom of the box.

My main concert is about the lights. For the moment I am planing on using 3 50W CFLs(1 on top 2 on the sides) for the seedling and the first 1-2 weeks of the vegetative cycle and then adding 125W HPS for the rest of the vegging and the flowering cycles while still using the CFLs as supplement lights to the HPS. My main concert: is this too much light? Or is it not enough? Should I go with just 23W CFLs instead of the 50W?

The other thing that I am really torn about is the soil. I guess there is something I don't get about the soil and fertilizer if you guys can point me to a good guide that will be greatly appreciated.
Here is what I came up with for the moment:
60% sterilized potting soil
15% perlite
10% wormcastings
10% soiless mix
5% premix NPK 12-6-6
My understanding is that using such a mix will most likely NOT require adding fertilizers down the road during the vegetative or flowering cycles( is that correct, or it depends on the plant) and how do I find out if this is the plant needs some extra nutrients.

Again I am looking to grow 1 to 2 Northern Lights plants, should I make the box smaller or get lower wattage lamps or this set up will work.

Thanks in advance and peace.