Just keep an eye on temp, if the bios allows it set a temp limit. 80C should be the absolute max I would let it get to. The AMD fans are a bit on the cheap side but I havn't had one not work out of the box, they do break easily and may not last (YMMV). A case fan is recommended, just watch your airflow. You don't want to add fans which couteract each other.
Power supplies, I always hear a lot of crap about power supplies. For a while there seemed to be no end to power supplie failures. It was like 1 in 3 would fail. But they have gotten better. They fail far less than they used to. I never noticed a great difference in power supply quality with different brands. In fact my last 2 power supply failures were enermax. Best advice, if it works and is stable use it, if not replace it.
Hard drive. I would have gone with serial ata. It does make a difference. Although the barracuda is a good drive.
The Nec 3550 is a good drive. I have had my best success with nec drive. The only time I end up replacing them is when I upgrade. Be careful with firmware hacks, they are the fastest way to turn a good burner into a lump of crap.
All in all I think you will probably be quite happy with your setup.