Well, I don’t know the specifics of what your light is made of, but the total watts is actually regulated by the driver. The driver can kind of be thought of as the ballast in a HID or maybe even a fluorescent light. It’s a transformer that usually transforms the standard AC current to most often DC current, but some LEDs run on AC current, but either way, the total voltage and amperage is converted and regulated to drive the LEDs at an appropriate level.
You might be able to drive the LEDs at a higher power by replacing the driver, or drivers, or you might be able to use the drivers in the unit to drive more efficient LED units. It could depend on many different factors.
Here is an interesting you-tube video where “growmau5” (pronounced Grow Mouse) does use a somewhat cheaper LED system, a MARSII Hydro LED and upgrades the LEDs in it, and this tutaorial, and his other tutorials might get you what you are looking for: