the higher priced cards are a pointless buy. the money you spend on the better cooler you could buy a higher tier card and get more performance for maybe a 2-3 c increase in temps.
if your getting a 750ti for power saving then you dont need the 6 pin model, thats for overclocking and boosting past reference.
if your set on the 750ti with a 6 pin just get the cheapest none reference cooler. the performance difference even oc'd will be minimal as most of the current coolers were designed with much higher tdp cards in mind.