I wouldn't recommend SSD drives, from experience they're quite a bit slower than 10k drives.
We've been testing them in our Data Centres and they've not been practical for I/O intensive uses.
Look up track seek times for the HD you're buying, that makes a huge difference in performance. The lower the better. Also higher rpm is faster.
RAID10 would give you redundancy as well as better throughput than RAID 5 if you're thinking of RAID at all.
As for processor, there are so many flavours its hard to keep track but whatever has the highest cache would perform well. A quad core or dual core would be minimum.
A graphics card with an HDMI output and an LED monitor with HDMI would also be ideal.
Also depends on your budget.
some indicative prices here if you're planning to assemble or want to have an idea for add-ons
http://msy.com.au/
Lastly, you'd need a Gigabit Ethernet adaptor if you ever want to transfer data over your LAN and/or a wireless N adaptor card. handy to have it in there.