When I finally get around to building the server, do you think it is worth going with SSD? Are they reliable enough to go without RAID? Does it speed up loading charts and imported items? Can I go with 128MB SSD for the OS and program and a conventional drive for internal backup?
I think that's a great idea. Get a couple 128GB Crucial M4 for $100 each today this weekend. RAID 1. No point in any higher RAID level. They will be roaring ha. Maybe a RAID 1 of 1TB drives for storage (which you can add later) and the 128GB for SBS and AC? Essentials needs about 60-80GB. The hybrid setup is pretty cost effective. Cheap mechanical storage with very fast flash-based loading.
Remember since it's less than 160GB you'll have to do a little tweaking.