I do not think you will have any problem.
1) The cubage of the case does not matter, in fact, a smaller case has a better cooling potential. The 140mm intake fan has almost the cooling surface of two 120mm fans. It can provide sufficient intake airflow. It is always possible to replace the fan with a higher cfm unit, at the expense of more noise.
2) The biggest need for cooling will come from the graphics card. The EVGA units are good, in that they exhaust the vga heat directly out the back of the case. Evga sells a $10 high flow bracket for GTX580, and I think it also may fit a GTX460. Check that out under accessories on their web site.
3) Do not count on the psu to help . It's job is to protect itself.
4) If you do not overclock, I think the stock cooler will do the job. Under load, it will ramp up and become noisier. If you replace it with an oem cooler that has a larger fan, the ramp up will be quieter. If you do overclock, I think you will still be OK. Considering how easy it is to do with the 750, I would try a modest OC.