The only problem I could see happening is if your power supply is not powerful enough to handle all the load, but you would need to determine that, and I'm not an expert on power requirements by any stretch of the imagination.
There are utilities that supposedly tell you what your power requirements are after you enter your system details, but I'm not sure how accurate they are.
http://www.extreme.outervision.com/psucalculator.jsp
Thats actaully not a bad calculator as long as 5 areas are carfully addressed:
1. You must make sure you match your devices correctly with the items in the lists it presents. Close is not good enough, especially with video card and cpu
2. If you intend to clock make sure you set the utilization to 100% and set the clocked Vcore to a higher number than you anticipate.
3. You must make sure you do not miss any fans or devices.
4. If you use the motherboard onboard NIC and sound onboard, add them in as cards
5. Add a minimum of 50 - 100watts to what ever the calculater totals
If that is followed the calculator is a very good way to measure a system