Timber grow lights make quite a few models with quality components other then that there are quantum boards prefab not exactly pretty though . You are already running on the low side most say you need 50 watts a sq ft with HPS. 30 watts a sq ft is what most recommend for LED. But I would say around 450 watts of quality led will match a HPS doubt your going to find a prefab designed to run 450 watts in a 4x5 though. This is designed for a 4x4 but still uses 600 watts http://timbergrowlights.com/redwood-vs/ So sounds like to me that if you want to shave off some heat you might have no other choice but to custom build.