That's a very difficult question. normal sizing is when you know applications size, num concurent users and increase the data in the application for a period of time.
the initial stages of the first server will be better because a higher frequency
but Xeon E5 2600 Famaly is the recommended processor. and this platform will be more scalable.
regarding the disk subsystem - click is not demanding of her speed. More important is the amount of RAM. The bigger, the better.
This CPU will be better for Qlik then 2620v4 and not particularly expensive