50kw isn't exactly nothing. I'll agree that being able to corner well makes for rapid progress over straight line speed if your not trying to be a complete idiot, but at the same time if your out on a spirited fun drive, having no go down the straights out out of the slow corners would be a real downer for me.
To me a fun car should be fun, so good handling and a bit of power. Not too much power as its suppoed to be fun, not hedge time. An IS with 160 odd Kw would be a cracking drive.
Unfortunately I am currently driving a 250kw SUV, it great on long drives comfy and plenty of power, and you can throw it down a B road, the opposite of what where talking about, ease it around the corners and storm down the straights... but fun, it is not.