It is important to get a lamp setup that fits your tent and plant setup.
We've made a video about this where we talk about grow tents, how light is contained and reflected inside a tent and how light intensity is affected by the size of the tent. If you plan to grow more than two plants in the future, you might want to go for a 4x4' tent, but if not, you might want to consider a smaller tent.
Our Z5 LED grow light covers a 2x2' (4sqft) area with high intensity for fruiting/flowering plants. 2x4' (8sqft) is twice that size and will require two Z5 lamps to achieve the same intensity. 4x4' (16 sqft) is four times as large and will require four lamps to cover the whole space with high intensity. We have just designed a new lamp that we call Q7. It covers 4x4' with high intensity and will be available on Amazon in around a month. This lamp is a perfect match if you're planning to cover a whole 4x4' area with high-light plants.
If you don't plan to grow more than two plants, I'd consider getting a 2x4' or even a 2x3' tent instead, as this will require fewer watts to achieve the same light intensity, and essentially be a lot cheaper. A large cannabis plant can take up anywhere from 10x10" to 4x4', it all depends on your grow style, what strain, how long you veg your plants and if you LST a lot. Two standard-large plants should fit well in a 2x4' space and in most cases, in a 2x3' tent as well.
It's attractive to go for a larger tent as the price difference is negligible.
But much like when we're buying shoes and a size 9 fits our feet, we won't buy a size 11 just because it is the same price. Having the right size will be a lot more beneficial than having the largest possible size.
I hope this information helped and steered you in the right direction. Light can be tricky to understand in the beginning and there are a lot of things to consider.