Bumping this post up again. Hoping the OP is still here as he has had posts from this year. If not hopefully this will help others. The AI Prime 16 HD and Kessil A80 are highly recommended for the Fluval Evo 13.5 gallon, but are they really that good for the tank?
IMHO - they are NOT. I love the Kessil A80, but the spread is awful. Having it on the Evo and testing PAR regularly it can barely go over 200 PAR in the upper tank areas without maxing out. The AI Prime 16 HD is definitely better, but the same issue persists! It is really lacking in spread on the Peninsula. If you want higher parts of your tank hitting 300+ PAR prepare to be replacing a lens 2x times a year, and replacing the light every couple years. Even maxed out the light can barely get to 300 PAR in upper portions of the tank. If you want all softies and LPS, and don't mind the sides of your tank being around 50 PAR this light will be okay. But there are definitely BETTER OPTIONS! It almost seems like both of these lights are more so made for 5-10 gallon cube tanks.. Remember this is from long term experience and extensive PAR testing on my end.
4 years into the EVO with an AI Prime 16 HD - I am ready to upgrade. This light has been quite problematic, and really isn't the best option. You have to work around its problems instead of it working around what you want. Personally I think even if slightly overkill the Hydra, Blades, XR15s, larger Nicrew/Hyggers, Meridian 11, etc are much better options. You could do multiple AI Primes, but fitting them in would be difficult, and more expensive.
Would you rather have a light maxing out on settings and still not strong enough? Or a light that is much stronger than what you need and gives you the ability to dial back the settings to find a sweet spot. All of you saying the XR15 is overkill of a light - it is a fantastic light for the Evo and IMO much better option than the ones you are listing.