I'm not sure how one might go about getting a reference 7850, but I would have to agree that pretty much any aftermarket cooler, or any that are put on by one of AMD's partners, are better for cooling than the reference one. All of the Sapphire cards I've seen have dual fans, so ~bonus~
Well, it's not like getting the reference 7850 is going to make your temps skyrocket. If you're on enough of a budget that 1k makes a difference (not sure which currency you're using), then the reference 7850 certainly isn't a ~bad~ way to go. Most people just prefer AMD's partners for their factory overclocks and better coolers.
To simplify: if your budget is that tight, go with the Amd ati radeon.