Yeah, 4x 3070's at least, 200w total for four of them, that might be stretching them to fully cover off a 3x3. If I were trying to cover a 3x3 I'd go 6x 3070's, total 300w and spread them evenly to cover off the 3x3'. That would grow some very nice bud. They get expensive, as expensive or more than higher end commercial panels, but they're the best you can get for indoor lighting right now imo. If you're on a budget, check out my thread to see what the LEC Sun Systems can do, that's $450-$490 to cover a 3x3 really well, heat is almost identical to LED's (I ran LED's in the same room before, and there's essentially no difference in temps). You can always start with 1x LEC and build the COB's over time to spread out the cost. The LEC/CMH + DIY COB's combo would be a nice mix and produce well. If you stick to these two options you won't be disappointed with the results, either will pay back your investment fast, first grow in a 3x3 would cover your cost + some.