[Elecraft] RTTY/PSK interface for the K3

[Adriano Perazio]

New on digi modes, i´m wondering what´s the benefits of adding an interface to the K3?
I´ve been working with the K3 “internal” interface and seems to work very well. I know there´s an offset when you work AFSK (this case) instead FSK and with a FSK interface it would zero beat.
Am i right? Any suggestions of interface?
Main application is contesting.

Tnx in advance 
PY2ADR / ZY2C
K3 # 4795 + P3 & getting another K3 next month.