As far as cooling and memory my rule of thumb is that if the reference board has cooling on the RAM, you should put coolers on the RAM (nVidia or ATi or whoever originally designed it, designed it that way for a reason). Generally it's just a passive sink on the reference boards, but some of them (like the 5800 Ultra) integrate it all into one sink that cools both the GPU and RAM. Either way, when going to BGA sinks like what you've put on, they benefit from airflow - which that style cooler will provide. Keep in mind that with a cooler like that, your case needs to be exhausting hot air that is generated by the card now, because you don't have a blower pushing said hot air straight out of the case. I know back in the day Zalman would include vented slot covers to address that, for example.
One other thing to note, since you've plugged that cooler into the card - the card's fan ramp is going to be designed around its stock cooler, so tweaking the settings a bit may improve either noise or temperatures.