1. That is higher than I would like. But it is tolerable if your regular day to day, non-benchmark temps are reasonable. What temp does it usually run when you are not stressing it.
2. 650rpm is pretty slow, why not add a second fan. In fact why not try two Nexus 120mm fans,
3. Try reseating the cooler and use a TIM that doesn't require a break in period.
4. 58-66 C is well below the 110C that these chips are designed for. 48 - 56C when not loaded, isn't that bad. And the 3770 has a reputation for running hot because of poor heat transfer from the chip to its casing. See: viewtopic.php?f=28&t=64782
5. It would be much worse with the stock cooler.