I'm ready to upgrade my 6 year old MacBook Pro to an iMac. My issue is that my iTunes library has just hit 2 TB and will continue to grow as I rip all my BR discs. I've been looking at getting the 3 TB Fusion drive so that it can hold my current iTunes library. When it's about to hit the 3 TB mark, I plan to get an external thunderbolt drive to connect to my iMac. My only concern is performance with the Fusion Drive. Will this growing iTunes library greatly impact performance while it's stored on the Fusion Drive? Or would it be best to get the 768 GB Flash drive as well as a 3 TB Thunderbolt drive (my existing external drive that my library is is connected via Firewire and about to reach it's limit) from the outset?