A single plant? A good 50w or 90w panel with real 1w LEDs driven at full power should do the trick. Avoid panels with white diodes, avoid anything with more than 7 bands (most plants, including cannabis, perform just fine with 2-4 bands,) and make sure they're drawing full power, as ultimately power in = light out.

Also, make sure at LEAST 25% of the panel is blue diodes. All those poor results seen all over youtube come from blue-poor panels. 10% blue is simply not enough.

I can't really make any recommendations.

Don't fall for the "Contains CREE!" diode nonsense and end up paying through the nose. Cree quit manufacturing some of the more important wavelengths and thus effectively eliminated themselves from the game, leaving Nichia, Bridgelux, Seoul Semiconductor, OSRAM, and several other companies to take care of it.