How about a 1000W MH instead. Better overall light spectrum and penetration.
Remember, you can never have too much light, only too much heat.
I personally don't care about efficiency because the value of the medicine far outweighs the cost of electricity.
Quality is the most important thing to me now. I don't really care how much stuff costs anymore. I try to find good deals but I never skimp when it comes to quality.
The more light you have, the denser/heavier your buds will be. You will also end up with quality buds over the whole plant and not just on top. Less popcorn.
StinkBud light motto:
Light is Right!