I would go with the clIf. Mine was super efficient. Never got got at .5 daily. We compared it to my buddies rd d9 and the d9 was .2 louder at .5 also. I have heard the 5750.1 isn't for a daily app.
I don't mind anaba groups older products when they had a different team looking after there stuff. Now it's owned by a crap company that has poor technical staff and are a bunch of idiots.
Go with the RD. Its a proven Zenon board. Same as the Atomic 5K, Cactus 5K, etc. Its a great amp and is fine for daily and will also do .5 daily on good electrical. The clif amp sucks. cant even compare the two.