Same for me - no desire for more. There is other things I would do now than power.
Not saying that the EX500 is too much for the chassis, it is probably a lot of fun and still pretty driveable. I doubt though that the car is much faster than an EX460 on a track. What really bothers me with it though is that its well beyond the limit of the gearbox and that you really need uprated engine internals. Imho with that you are getting into power dimensions were you might run the risk of just have one issue after another and very little gain in lap time if any.
My next steps would be stronger clutch, short ratio gearbox (5th and 6th are way too long) and next level of suspension (some kind of 3way) that also enables a higher camber setting (not sure if this would be Oehlins, Nitron or maybe even KW Competition) ... then I want the wheel arch vents to improve front downforce...
Not sure if a turbo conversion really would be cheaper - If you want something that is sustainable on a race track you will need cooling also on the Turbo.... and uprated internals will be necessary as well.