[DAEMANO]

Speaking solely in terms of a Fiat, the performance bargain is the straight 500 Turbo model (not the Abarth). It's $19,500 base with the same engine as the Abarth, just detuned (or lacking of the extra grunt provided by the ECU when pressing the Abarth's sport button).So a track build with a base 500 Turbo would look something like this.

2477 lbs / 2387 lbs (w/rear seat delete)
203 HP / 239 lb.ft TQ

$19,500 Fiat 500 Turbo MSRP (new)
+$900 Dyno-comp Stg 1 ECU Tune
+$850 Koni shocks & Springs combo or ST Coilovers
+$950 Wilwood BBK
+$600 Summer/Track tires (16" will do). Your choice.
$22,800 Fiat 500 "USA Competion Spec"

This would be a beast at the Auto-X or track. No it wouldn't offer the pure driving pleasure of an FRS/BRZ/86. However if we're going to toss cars like the high COG, front drive Fiesta ST ($22,195 msrp, 2700 lbs, 197 hp, 202 lb.ft tq) against a Fiat, dollar for dollar new an upgraded Fiat 500 Turbo would absolutely smoke the Ford. It's 400 lbs lighter, and has more HP and TQ.

As far as new cars go, an upgraded 500 Turbo may actually be the current performance bargain king if we're talking purely about lap times per dollar. Now that sounds strange, but for these prices I'd love to see another new equipped so well, weigh so little, and have so much power. Otherwise, on the strength of it's chassis dynamics, platform, and aftermarket, give me an '86 all day.