The only problem is, I don't have that kind of money yet. Well... that's a lie.. I do - however I feel spending nearly all I have on lights to be a bit ludicrous...
Surely it would be better for my position at the moment to stick with the HPS+Cool-Hood. Atleast it's second best, right?
I'm still going to pull good numbers with my 4x4/600w regardless if I don't use COBs, then I upgrade from then on out
They are expensive for sure! Especially when compared to hps. I have nearly always used 600w hps, These diy cob builds are new to me, just came across them a few months back and thought wow, then worked out the pricing and thought sheeeet!!
You will be fine with your 600w if you have them and all the hoods bought. once your several grow down the road you may or may not want to change. That's all down to you.
At the end of the day I have had many many grows under hps and have great quality and yields.
These guys building DIY lights are pushing the quality and yields and efficiency to the limits and doing some amazing things. To give an idea, someone who used hps and was getting an average of 0.8 grams per watt is now getting 1.9 grams per watt using the same space and growing methods. But the cost for someone starting to grow is high.
I will be joining the league of exceptional lighting brigade myself soon enough. But all in all you will do great things with the set up you have and will be very happy with the results, I promise!
And just a point on Canna A+B, yeah you can use jacks, yeah you can even make your own at a fraction of the cost,but at the end of the day how much is a 5ltr bottle of A+B in comparison to the amount of runs you will get from those bottles.. especially if your hitting a pound a run in a 4x4... Its nothing. If you grow 4 warehouses full then yeah every penny on nutrients adds up but if its a pound or two here and there canna is reliable and simple and not expensive. Not that I would knock anyone wanting to save a buck!