Go for it. I have the Pro Stick Plus as well and a clean spectrum nearby. Despite this I bought the Uputronics SAW preamp for the extra gain and installed it at the receiver end for convenience. It gave a big increase in messages, aircraft and range. I’m very pleased with it.
After installing I saw the benefits straight away. But after some experimentation I got a slight improvement again by changing the gain in PiAware, from the default -10 (max/AGC) to 49.6 (the next one down). This is because the preamp introduced a bit of in-band noise which was drowning out some of the weaker signals, and dropping the gain a touch sorted it out.
As you can see from the photo I’m powering the preamp from a USB port on the RPi. It works no problems. I’m using the official 2.5A RPi PSU.