Nice build.
You could replace the Velociraptors with an SSD to reduce heat, power consumption, and improve airflow (by freeing up space inside and reducing the number of cables).
I've done similar builds for some clients. I usually get a
black Netvista casing though. They're used for basic office tasks, so I don't have to put high-end parts in them--my last build was an Ivy Bridge Pentium G2020 with an H61 board and 4GB RAM.
I don't have to worry much about heat buildup, but install an 80mm exhaust fan just in case.