Storage on 7i5 BNH

I have nearly 2TB of Flacs and growing .
Would it be better/cheaper to go with internal storage or just external USB 3 HD?
I understand i can only go to 2TB internally 2.5"HD.Or should i go just external USBs which are quite cheap at he moment.
Do the external HDs have to be powered (is there a supply from the USB) Can get 4TB for less than £100.
Any benefits from one or the other?
Don’t really want the expense of SSDs

depending on your case, you might be able to fit a 5TB seagate (check the max height though).

Ive seen the 5TB baracuda but its 15mm thick