Well I wouldn't recommend a new machine at all because it's a learning exercise. If you had
to build a new machine these would be my comments:
Firstly be mindful of your units lower case b is bits whereas upper case is bytes. 8x difference between the two.
I've seen nothing to suggest to me that anything under 2.6GHz won't achieve "n" amounts of data transfer.
I doubt you'll see actual differences between triple channel and dual channel out with a benchmark.
No graphics required but you'll obviously need something to set it up so either a motherboard with onboard GPU or a low powered GPU you can remove later.
That PSU number seems pulled out the air. Where are you getting 600W from?
RAID for the fun? Are you mad?
Would you want hardware raid or software raid?