jellyfish.. which ones you have??? i got the 300w, and if u go by their wattage, the '3' i had should be suff (or close to it) for a 4x3.5ft tent- they were woefully inadequate...
I use the 450 Model, which, according to Viparspectra's instructions, "is designed to cover a 2.5 X 2.5 feet area." I use one 450 in a 3X3 area, and it works fine.
If you have a4X3.5 ft. tent, you need at least a 450, or you might need two 300's.