You have a NH-D14 but you think it isn't working properly? What? Are you sure it's compatible or fitted correctly? This cooler is probably one of the best air coolers in the market... we can't really recommend anything else except for a custom loop, closed loop or a different air-cooler that will give you slightly cooler temps (talking about 1-4c here). Before you buy anything make sure you properly installed the cooler and if there is something wrong you can always replace whats needed (fans, backplates, screws etc.) buy buying it or talking to Noctua's customer service. If nothing works out just return it where you got it from and get something like an H100, X60 or a new version of the Noctua.