I have an evolve 4 with the smaller version LEDs. In my experience with the tanks (i have two of these) the stock led's are sufficient for growing beautiful thick moss and medium light plants.
During my trim and WC last night, i noticed that my original effort to plant HC, which didnt take off, had managed to established itself in my moss tree as i saw light green patches on the moss itself.
You can certainly get one of those clip on cfl lights from fluval, finnex which would work a bit better than our led's but i was never entirely sure whether the dimmensions would fit or over hang my 4 gallon tank. im sure you wont have that concern since your 8 is much larger. which reminds me, i have to email aqueon again as my LED light is starting to flicker. better get this sorted as it makes me and likely my shrimp very uncomfortable.
"I am Groot", the faithful protector