Heads up for a SSD as system drive! 
My vintage Intel Mac Pro 2006 8-cores feels fastest than my brand new MacBook Air. Everything works smooth and fast, 20 seconds for booting, programs needs 1/5th of time to open. No regrets, so far (3 weeks).
In fact, I’m thinking to sell my firewire work RAID for a SSD, just to avoid noise and speed things up.