When I first made my purchase (scion fr-s, no the gt-86... we're cursed with the scion over here), I too started worrying that I made the "wrong decision" in buying this car. I was always a huge v8 lover, and was a number cruncher. I'd spend my free time trying to figure out how much faster x car would be at x track, and so on.
So, I had a little bit of a worry in the back of my mind that I made the wrong choice. After seeing all these videos of the v6 mustang beating the fr-s around the track, the focus st beating it, etc. I could feel my ego being threatened

.
But then I figured - if I sold this car I would regret it so much later down the ride! No other car I've been in has put this huge of a smile on my face, each and every time I drive it. Who cares if its "underpowered"? Not only that, but when I pay off the car I'll be able to start putting money towards forced induction and making this car faster.
So, I guess it all comes down to - what do you want? Do you like the car? Do you see yourself enjoying the car for years to come? Do you get up on a saturday and want to take the car out for a nice drive through the canyons? Does it put a smile on your face whenever you drive ite?
I answered yes to all the above questions, and obvsiously I've resolved this car is just perfect

. I'll always have the chance to buy some beater v8 car in the future, but right now I'm just enjoying this wonderful car.
I think I'm going to go for a drive now, lol.
EDIT: If your talking about practicality - that makes sense. But it comes down to, is it livable with on a daily basis for your current lifestyle? Your girlfriend has her own gt-86, so why not just take both cars out wherever you go? That'd be driving in style

. I wish my girlfriend wanted an fr-s, I'd buy another one, LOL.