The way we think about what light fits a certain space is by looking at lamps' light output, i.e. their light footprint. In other words, how intense light is projected over an area.
If you're not familiar with "light footprint maps" or "PPFD maps/charts", I suggest you ask Google. In short, a light footprint map will show how intense light hits a certain area.
If the term PPFD is unfamiliar to you, the short explanation is that it's a description of light intensity (photon density). Higher PPFD = more light.
We know that mature cannabis plants thrive when subjected to PPFD levels of 600-900 µmol/m2/s.
Grow light brands will show light footprint maps of their lamps where the PPFD (light intensity) has been measured in various spots across said area.
You said you have a have a Vipar 600W? This one, right?
The fourth image in the listing is a light footprint map:
Here we see how the light spreads over a 3x3' area at 22" height. We see that the very center spot PPFD value is 736 µmol/m2/s, which is good, but we also see that the light intensity drops fairly quickly. PPFD values below 200 µmol/m2/s barely drive photosynthesis.
Ideally, you want PPFD levels as close as possible to the maximum your plants can take over the same size area as your plants occupy.
Compare the map above to our Q7's light footprint map:
View attachment 4816071
These lamps are obviously in different price categories but I still think the maps serve as an example of how to think when comparing different lamps or when trying to decide which lamp is right for your space. Usually, the more light a lamp emits the more powerful it needs to be, which means it will cost accordingly. The choice of lamp most often comes down to how much you're willing to spend in relation to what performance you expect from the lamp.
Finding various lamps in your price range then comparing their light footprint maps and selecting the one that has the best values is a good starting point.
Hope this helps!