It depends on you goals.
If you want full control with map switching on the fly and flex fuel etc, then it is definitely a great upgrade together with the right tuner.
If you run non-VTG turbos then the Syvecs will control boost for you yes. You do not need, or want, the Plex boost controller. I run boost by gear with inputs from a lot of stuff (ethanol content, speed, slip, map number etc) and it works great!