Give us some more data before you start tinkering and buying?
Please give us a log from MSI afterburner or a screenshot of the stats while gaming. Its helpful to know whether your GPU is throttling a little bit, or throttling really hard. That will tell you how much you need to fix.
84C means you're hitting the soft limit, the driver will try to reduce voltage and clocks to get below 84C, or hover just under it. It can do that in two ways, hard cutoff and dropping a few hundred mhz (big perf hit) or with small intervals called 'boost bins' of 13mhz. The latter is what you want, even if you can't get the temp that much lower than 84C. The GPU will then run happily every day.
If the standard fan curve gets you to these temps, just adjusting fan curve won't save you, that is for sure. Unless you like sitting next to a hair dryer all day...