Suppose it depends on supporting mods too (and that includes the driver lol), as well as what torque goes with the Bhp and how much of the power is "under the curve" as opposed to just "headline figures" (and how progressively it is delivered)...
With suspension improvements, better brakes, better tyres, more aggressive geo setup etc... the power can increase...
Bog standard then 280/300Bhp (and similar lbs/ft torque) for Classic, and 300/320Bhp New Age is plenty for most IMO.
My Hawk has standard brakes (yellow EBC pads), standard shocks and springs, quality road tyres in 235/45/17, but uprated droplinks and ALK...
It's running around 325Bhp and 538Nm (397Lbs/ft) (Deltadash mapped by BRD), which is not "that" high in bhp but the torque makes up for it and is available over a wide rev band (power comes in at 2500-2600rpm, max torque at 3400rpm, and power builds till about 5800-6000rpm, and after that tappers off and better to grab another gear from about 5500 on).
It is at an enjoyable power level now... although I'd say the car could do with another 30-40 bhp and maybe another 20-30 lbs/ft without detracting from that enjoyment (probably make it even more enjoyable in fact). After that it will need better brakes, full poly bush treatment and more aggressive geo setup to remain enjoyable and controllable at my personal driving skill level (other more skilful pilots might feel more confident and would happily carry more power without wanting/needing control mods).
The v3 Classic I previously had was running around 320bhp and 310 lbs/ft (dyno'd and mapped by JGM with very progressive power delivery and plenty "under the curve")... fully poly bushed, uprated droplinks, ALK, Tein suspension, DSP2500 pads with standard brakes, aggressive geo setup. I found it very enjoyable at that power level and felt "more alive" than the hawk. It probably could have also taken another 30-40 bhp as well as torque, but not much more without first upgrading the driver. At the power level it was at it was possible to "loosen" the back end in the corner to get some oversteer to tuck it in, but in a very controllable way... allowing to tuck in the car and partially "steer" with the loud-pedal. Keep in mind it was only running 215/45/17 quality road tyres, so plenty scope to improve traction was left.