As far as your cooling goes, although the CPU is very important (esp if you're overclocking), getting heat out of the case is just as critical. Getting cool air in is also important. To this end, you may want to look at aftermarket case fans.
For your hard drives, you can easily have 2 HDD's so no need to worry about that. If you down the RAID route then you will need to do that when you install your operating system. Talking about operating systems, I'm assuming you're going down the 64 bit route (as you are getting 6gb RAM) so check to see if the applcations you use will run properly. Chances are that you will be ok, but it's worth the time to check.
I've got an LG Blu-Ray rewriter that I use on my main PC. It can be a tad noisy but has given me faultless performance.