I've just spent weeks with a mate trying to get some seats for a Mitsi Evo, and be very careful what you do.
Firstly, I'd be surprised if you can get a decent set of sports seats for less than £500.
Secondly, make sure you get decent subframes (and factor in that price) as the cheaper ones we tried are real crap to slide the seat on.
Watch out for the seat "ears" - some of them will be too high/wide for the car. Make sure the base of the seat will fit around your centre console and still allow for slide.
If you can, get the same manufacturer's subframes as well as seats - even those that say "Sparco fit" or "Recaro fit" are never perfect.
The best way is to actually go to a place who has them and will let you come down for a day to try them out - firstly sit in them; it's surprising how uncomfortable some seats can be if they don't fit your arse properly. Secondly make sure you know how to remove/replace your seats and try sitting one of the new seats in your car before buying it. Any decent place will understand you want them to fit and won't mind as long as you don't scratch them - however I think my mate's spent well over a couple of hundred quid just in postage back & forth on three or four sets before we found one that fitted properly.
Bear in mind these were proper racing bucket seats, but the points remain the same.
Best of luck...
O.
