I've actually done this
I've installed 4 1W highpower LED's and 2 3W highpower LEDs in my terrarium. THese are FAR FAR FAR better than those "normal" 5mm LEDS one 3W led emmits 100lm in an angle of 110 degrees. Comparred to using the normal 5mm LEDs you get a higher output pr. Watt, and it is very much easier to replace one of these than 70 "normal" LEDs
The type called Seoul p4 is really good! And you can get them in several different colors. For now I've tried using a combination of warm and cool white and a "natural white" this gives me wavelengths mostly in the 450nm area and from 600-650nm.
As I've read - these highpower LEDs are the future of LED lighting!