I tested out the 620. I really disliked it. The temperatures weren't much better and at times worse then the air coolers I've used. But the main thing that led me to ripping out the 620 and returning it asap was the pump's clicking noise. Drove me nuts. Sounded like little pebbles being moved around constantly.
Can't say much about the 812 as I haven't tested that. I have tested and can recommend the thermal right venomous X, and noctua cooler master D14.