I don't see how there could be much of a difference between a single 8 bulb or (2) 4 bulbs, other than you could spread out the (2) 4 bulbs for slightly more sq ft coverage..it would be negligible IMO. Either setup will only cover an appx 2' x 4' area..you could do a SOG with 32 small clones - 1 clone per 6" sq - or you could grow a few big plants. I can fit 6 in 5 gal buckets under my light, comfortably, probably 9 if i wanted to push the outer edges of my light spread
IDK what it takes to get 2lbs in a 4x4..or if it's even possible. Most people are happy to get 1 lb in that sized area.
2 600's will have more heat but it won't be as concentrated, unless maybe you were running a dual bulb hood. I run 2 600's in cooltubes because i don't have the height to get 1K's up high enough from the canopy. I don't see 2 600's fitting in a 4x4..the 1K will probably be better, just going to need a good fan to cool it.
