Well, I've only driven one fc (our '87 track car), and it doesn't have a whole ton in the low end, but it revs up FAST (way faster than my miata) and in its mostly stock configuration has a lot more guts than my mx-5. I thought I knew what power oversteer felt like before, but after taking the fc out on the course a couple times now that we've got it restored to almost stock condition, I realise I've got a ton to learn, since I can now start to learn how to steer with the gas pedal
As far as handling, even stock, the FC's chassis is sooooo much stiffer than my miata. We upgraded to some tanabe springs and kyb gas shocks, got some shock tower mount braces, and the car feels far flatter in the slaloms than my MX5. After we added the camber plates and got a decent alignment set up, the thing just had grip everywhere... feels way more nimble than my miata, despite weighing about 500 lbs heavier. (tho we're starting to work on weight reduction now
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As far as potential motor-wise... just depends on how much time/energy and money you want to dump into it, and if you plan on going turbo or not. If staying N/A, theres a lot of stuff you can work with... depending on how crazy you want to get. You can get a p-port/bridgeport job done to add a lot of power, switch from the stock steel to carbon apex seals (will require more frequent rebuilds, but allows the engine to rev above 8500 rpm)... you can get lightened rotors, and I've even been told you can switch to the RX8's higher compression rotors. If you don't care about emissions, you can gain a lot by upgrading the exhaust system (both weight and power wise - our car has 3 catalytic converters stock! very restrictive and heavy!)
If you want to get really nutty, the sky really is the limit... I know of at least one 3-rotor design w/a single turbo setup pushing over 1000 bhp.