Watts is a little outdated when it comes to measuring effectiveness of lights for plants now -- most people now look at PAR as the best measure.
Here's a good thread on that: Lighting an Aquarium with PAR instead of Watts
I don't have a tremendous amount of experience with many sorts of lights (I have put in some research into the subject though ) but one that I would recommend is the Finnex Fugeray (Amazon.com: Finnex FugeRay Aquarium LED Light Plus Moonlights, 20-Inch: Pet Supplies). It is the light that I currently run on my 10g and it gives me light in the medium range. You pay maybe slightly more upfront but because it's an LED you never have to worry about replacing bulbs so you save more in the long term. $61.49 with free shipping really is a pretty good deal anyway too.
Values between 10-30 are considered low light.
Values between 30-80 are considered medium light.
Values between 80-120 are considered high light.
(Source: PAR vs Distance, T5, T12, PC - New Chart)
Here's a good thread on that: Lighting an Aquarium with PAR instead of Watts
I don't have a tremendous amount of experience with many sorts of lights (I have put in some research into the subject though ) but one that I would recommend is the Finnex Fugeray (Amazon.com: Finnex FugeRay Aquarium LED Light Plus Moonlights, 20-Inch: Pet Supplies). It is the light that I currently run on my 10g and it gives me light in the medium range. You pay maybe slightly more upfront but because it's an LED you never have to worry about replacing bulbs so you save more in the long term. $61.49 with free shipping really is a pretty good deal anyway too.
Values between 10-30 are considered low light.
Values between 30-80 are considered medium light.
Values between 80-120 are considered high light.
(Source: PAR vs Distance, T5, T12, PC - New Chart)