Welcome to the seacoast! My name is Ty and I live in Portsmouth as well. I do try to organize events but all our schedules usually stink, however we will make a meet happen soon.
If you are looking to get parts installed I would recommend Wicked Cas in Kingston if you want to stay local and go to a reliable subaru shop. They can install and tune everything.
The best car audio place around is the Audio Barn in Exeter. They are right off of 101.
I had Lou's do an exhaust on my integra last year and it was great quality and quick but past the actual exhaust i wouldnt really recommend them. I know they dabble into other parts but I would stick with an actual tuner shop.