Yeah, Dude, 2 600 watt HPS would be very nice... you could run the two lamps over 4 or 6 sites and do pretty well, all 8 sites???maybe... In hydro the idea is efficiency, yield, and trying to eliminate waste ESPECIALLY in nutrients. That is a big reservoir, you are going to have to factor that into how you manage nutrients if you aren't gonna match the capabilities of the system with lights.. It will be way easier to limit plant quantity based on light output, so, say you run 2 600watt HPS lamps over 4 sites which I think is a good matchup, you will only need to use half of your reservoir and half of the nutrients... There is no point in wasting nutrients on poorly lit plants.. IMO, plant what you can properly light, and properly feed what you plant and you will do way better than planting what you cannot properly light and wasting nutrients on half of the crop. 2 600 watt lamps and 4 plants could net you ~40 OZ with your $$nutrients spent on well lit plants. With 2 600 watt lamps and 8 plants with a net of maybe 60 OZ where you spend more $ on nutrients and get maybe 20 more OZ of stretchy fluffy crap bud, not to mention the possibility of nutrient imbalances caused by the extra 4 sites impacting the results of the sites that are well lit... Moral of my story, if you can only afford to do a few the right way you will benefit more than half assing all 8...