It's ok to want 300rwhp, just depends what it's going to be doing IMO
For example, skidpan days it would be good fun, or really tight hillruns (the type where you question having a 1500kg skyline in the first place) it would also be good at.
Can't see it being fun anywhere else though! But of course it's all personal taste.
I definatly agree, get something with headroom for later, the power bug bites all.