I haven't done anything t my Impreza either. I think the most I will do is eventually get a strut tower brace but even that right now isn't high on my list. I would LOVE to get say a Borla cat back but I don't think any company has a cat back just an axle back. I haven't gone shit to my Legacy either.I had a "CAI" in my bmw which was running a tune. the CAI made it sound nicer but my intake temps were going up so I put the stock airbox back on and bought a dry afe filter. temps dropped back to normal. I haven't decided if I'm going to do anything other than stock in my daughter's impreza. i don't need her to have performance. that's why i bought her the impreza. lol
Now, My S4 is a different story. I had a lot of work done years and years ago and now I NEED to have work done. I put in a turbo back exhaust which included 1 cat per pipe instead of 2, bigger diameter pipes all the way, upgraded intercoolers, second oil cooler, engine tune, trans tune and Bilstein PSS9 C/Os. Now, I have bad UCAs front and rear, a bad turbo, a pre-cat exhaust leak and possibly bat cats. While I have the money to fix it, I want to do it right and put new bigger turbos in, stiffen up the chassis, maybe eventually a 6-sp swap, brake upgrade, internal engine upgrades and tune, etc... but I have kids now and can't really drop that money without getting divorced. Car has been sitting in my garage since maybe 2018 with a random start and move here and there. Oh and the fabric on the roof is falling and that annoys the shot out of me for some unknown reason.
But I guess my point is the S4 had a LOT of upgrades available and the tuning potential is great. The Impreza, well that is a different story!