I am confident that you will find AutoCOBs or other COBs and the Amare LED/COB lights already cited to be among both your best and cost-effective options. If you want to stick with aging LED technology, there are many good options there, but these will simply run hot, suck power, be noisy, etc. compared to COBs, besides costing more.
Perhaps, consider AutoCOBs (see cobshop.net), say a set of 4. For what you get, pure performance (PAR) per buck, I can't think of anything that will beat them. Most other options that will give you high quality performance and results will likely cost 2x as much or more. And besides doing a good job with the plants, with COBs you get bonuses of less heat, electricity use, no noise/fans, and each can be independently positioned.