If the adjustment of the GPU fan - if at all possible - hasn't produced good enough results, then a fan swap is probably a decent way forward.
Although slightly ghetto-ish, taking the fan and fan shroud off, strapping on a 140/120mm fan with zip ties and connecting it to the motherboard could be enough cooling. It is only a 60W TDP card after all. Hopefully motherboard fan control should allow you to adjust it to your noise/temperature liking.
I have done exactly that with my MSI 750Ti and the 140mm cooler of my Thermalright HR-02 Macho. But in a m-ITX case that might be difficult... The built in fan was unbearably loud for me even at the slowest speed since otherwise I don't have any fans running except the PSU which is quite quiet.
Before I applied this solution, I had another ghetto-ish solution. I disconnected the fan from the GPU-PCB and connected it with jumper wires to the fan controller of my case (3 Modes: 0V, 6V, 12V). As long as I don't run any games, the GPU stays well below 60°C without any fans running. The loud fan only had to spin while gaming when I don't care as much about a silent PC.
Your mileage may wary because I have a huge case with lots of vents without a hot CPU etc. But at least my 750Ti with a quiet 140mm fan and SpeedFan is inaudible as long as I don't have furmark running. The only time I can hear the fan is when the GPU goes over 70°C and the fan is starting. It then revs up to about 800-900 rpm for a few seconds until the temp is down to under 70°C where the fan continues to run with 500-600 rpm and is inaudible and shuts down when the temps go under 60°C. This works great so far, but I haven't done any real gaming with this new setup.