1) Are parts I have chosen compatible with each other? (Also, will they fit in the case?)
2) Is there a better choice for something, such as a cheaper item that has equivalent capabilities?
3) I'm thinking of setting up RAID 5 by purchasing a pair of 2 TB drives that complement my current 2 TB drive. Is this a reasonable idea, and what manufacturer is most reliable these days?
The parts I'm the most iffy about are the PSU and SSD, since I have little experience with either.
Overall in my personal opionion this is one of the best HPTC setups I have seen and without the options it is cheaper than your original build. It will also perform much better on all fronts. I'm sorry about sorta throwing your ideas to the curb but I have done a lot of studying about computer parts and the AMD seems to be the way to go.