you could, but then heat would be a VERY large issue.
one of the main problems currently is heat, and that's with 3 watters, not 5 watters. a K2 would probably work, but i don't know of the optics would work with them. it might be that the max you can put in is 3 lux 3s.
keep in mind batteries too. with 3 3 watters, you need around 10 volts, with 3 5 watters, you'd need around 18 :o