Welcome to the club!!! I'm also rocking a GX and it really is a case of they go alright for the power they have, just don't try racing anything over a 1.2 diesel...
In terms of looks you can be really refined, or really bonkers, the great thing about them is number of parts that fit from the WRX model because the chassis code is the same.
I bought mine with green wheels and as I found recently it also has a green neon strip under the rear bumper, so I've decided I'm going to start greening out the car.
I can't say id recommend making it look like a full STI replica because you'll constantly have people trying it on with you and chances are you'll get pulled on by a civic or some nonsense.
But yeah like Matt said ^ alloys, lows, tints and maybe even a front lip and rear diffuser as a good start point
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