by special request...
When choosing a power supply there are three variables you must consider.
2. Type of voltage
3. Amperage rating
1&2). Voltage, your typical PC fans are made for 12 volts, and this is 12 vdc (second criteria). DC stands for direct current. The other one you are likely to encounter is AC, which stands for Alternating current. These two are not interchangable... its got to be DC output. The voltage rating we can vary a little and not cause any issue... but its best to stay with 12-13.8 volts.
3). Amperage is another critical rating. This is a measurement of current flow... think of liquid water flowing through a line. If ths source of the water pressure does not have enough flow capacity, the pressure in the line will drop as flow rate increases... The same holds true for amperage and voltage. If your wall pack doesn't have enough amperage capacity, it wont be able to maintain its rated voltage under load. It will overheat from the excessive loading and soon fry itself.
We can have a wall pack rated higher in amperage than we need but not lower.
The rating that you will need depends on the fans that you run. Each fan will have its own rating... lets say yo have two fans. Fan "A" needs 12vdc @0.5 amps while Fan "B" needs 12vdc @0.75amps.
For continuous use you should always use a power supply with an amperage rating twice what you need.
So in our example we would need a wall pack rating of 12vdc @ an amperage of ( (0.5+0.75)x2) =2.5amps
In critical applications (your helis are within inches of your 6 bulb T5)...it is always best to have at least 2 smaller fans and 2 power supplies instead of one large fan and supply. That way if one fails you will only lose part of your ventilation and not all of it.
The cost of two smaller fans and two power supplies over one larger setup is much less then the cost of just one expensive plant.