It's like my dad always said, "if you want a fast car, buy a fast car. Don't buy a slow car and try to make it fast."
If you want the most horsepower, there are plenty of turbo options. Full Blown and Vortech are popular options. The problem with adding this much power is that the frs isn't designed for it. So going over 300whp, you will need to start looking at new clutches and other internal bits. You will also need a bigger, high flowing 2.5" or 3" exhaust. I read somewhere from someone who turbo'd their 86 that they needed softer suspension in the rear because they could never get any grip. Coilovers are definitely the better option for this since they're adjustable, but obviously they cost more. Look into Buddy Club and the KW V3s. I hear a lot of people talk about Stance coilovers but idk how good they are.
The most important mod will be tires. If you're going for mad HP, you will want more performance-oriented tires, like Dunlop Direzza Star Specs or Hankook RS3s. As for rims, Enkei RPF1s seem popular. But that's really an opinion thing.