@jonny,
Welcome to ILGM you have just joined the fastest growing forum on the net today. The fokes here are more than willing to help you with any problem. They are also very friendly people. And you have to visit our Lounge this is where we talk about other things besides growing. Its a get to know each other thing.
OK light…
If you are needing to save some money and want to get only one light get the one 125 watt CFL (compact fluorscent light) and get it in the 6500 K spectrum, it will do fine in blooming flowering as well as vegetative growing. Yes it should do very well for that size canopy/floor space. With CFL lights you can do a real easy in your head estimation of about a minimum of 40 to 50 watts per square foot, and so actually about 125 watt. actually might be over kill, but it depends on how you are to mount the light, how much vertical space it will take up and if you can keep the temps down in such a small space. Even in a fluorescent light, 125 watts will put out quite an amount of heat.
The five 20 watt CFLs might be a better option for such a small grow but you might not save anything on heat. And in fact it may create more heat. Most of the heat with fluorescent lights comes from the ballast. In a CFL, this ballast is inside the vented plastic base. With so many lights, you have a whole lot of little ballasts that total wattage is 100 watts but the extra numbers of ballasts might create more heat than the one ballast in the 125 watt bulb. You might want to look into finding one 100 watt CFL in the 6500K for you size grow.
Here is some more information on fluorescent lights:
http://www.nodakelectric.com/energy-saving-lighting-tips/20
MacGyverStonerBergman’s Lab Science Officer
Posted by garrigan62
First I’m going to give you the link to the " The Grow Bible ". You can download it for free. A wealth of info for beginners. Here’s the link…
Also if you could this would be a big help …copy and paste this " SUPPORT TICKET "
Here is a he link
COPY/PASTE: This “Support Ticket” into your forum post.
named these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA
Strain; Type, Bag seed, or NA
Soil in pots, Hydroponic, or Coco?
System type?
PH of runoff or solution in reservoir?
What is strength of nutrient mix? EC, or TDS
Indoor or Outdoor
Light system, size?
Temps; Day, Night
Humidity; Day, Night
Ventilation system; Yes, No, Size
AC, Humidifier, De-humidifier,
Co2; Yes, No
Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the
questions and facts will help us help you 
We had a previous Support Ticket posted, but lost it during the "da
have this older more detailed support ticket that I saved and added to awhile back:
Fill out a “Support Ticket”
COPY/PASTE: This “Support Ticket” into your forum post.
Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA
ILGM Support Ticket:
What is the strain and type(unknown bag seed, strain name, regular seeds, feminized seeds, auto-flower, etc)?
Indoor or Outdoor? If outdoor, planted
in ground or in a container?
Size of space (max height and area, length/width)?
Soil or Hydro? Type of Medium used? System type?
pH? Of the soil or medium (root zone/reservoir/run-off) and of the water and/or nutrient mix that is fed to the plant?
Type and strength of nutrients used? NPK? EC/TDS/PPM levels? Of what you feed it as well as what is in the water by itself and in the soil/medium (run-off), or reservoir.
Temperature? Day vs. night temp or highest and lowest temps? Root zone temps?
Humidity %? Day vs. night
Light system/watts/lumens/FLUX/PAR?
Ventilation system? Size? CFM? CO2? AC, Humidifier, De-humidifier?
Number “weeks/days” from into Season, Vegetative Growth or
Bloom/flowering?
Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but try to be brief and to the point. Short and to the point questions and/or facts will help us help you 
~MacG. Science Officer
Posted by garrigan62
Johnny, I now its a bit much but its what you asked for. 
I hope this helps
If you need anymore help with the info just let me know I’m here for ya
B Safe
Wil