i can't say anything about the Zalman aftermarket GPU coolers b/c i've never used any of them. but i have used several Arctic Cooling products - namely an Accelero Xtreme PLUS, a few Accelero Xtreme PLUS II's, and several Accelero Twin Turbo II's - and i swear by them all. unfortunately i have nothing to compare them too except for the OE reference coolers they replaced. that said, i've used them to cool an HD 5870, several HD 6950's, a few GTX 460's, and several GTX 560 Ti's just in the last 2 years. even during maximum load crunching 24/7 on any of those video cards, i never had to run the fans on any of the various Arctic Cooling products higher than 50%. the highest temps i saw on any card was 70°C, and the average temps i saw were closer to 60-65°C. mind you none of the dual-fan or triple-fan Arctic Cooling models actually make noticeable noise until the fan hits 55% or so, and that's coming from a noise freak...so if you ask the average person, they'll probably tell you that they don't here the thing until fan speed reaches 70% or so.
as for that samsung RAM on amazon right now, i can vouch for its excellence. the stock timings look dreadful (11-11-11-41-2T) for DDR 1600, but they're very misleading. i'm running 2 x 4GB sticks in each of my machines right now, and while my timings are still quite conservative (8-8-8-30-1T @ 1.35v...and they're rock solid), others are reaching quite high clock speeds and quite low timings.