You really only need a performance boost if you do multiple deploy or multiple upload tasks at the same time. If you are just looking to add storage, you can easily put in a bigger drive. If you want to span multiple drives, you’ll have to look at implementing some form of RAID.
Using a NAS, connected via the network card, would probably slow down your imaging process even to one machine unless you have a dedicated NIC for the NAS, and a dedicated one for the client network.