I think you are kinda missing the point. Its not whether or not its worth racing or not, its rising to the challenge of a race. If the 525i has the gumption to race a GTP, are you just going to let him drive by or put him down?

Crap man, its not always about who has the biggest motor, the most hp, torque etc. Sometimes its just for the fun of it. To mash that throttle, hear the car wind up and in the case of a GTP the blower whine and so on. Most of the time, on the street anyway, its about knowing your car. From a roll its all about whether or not you are in your powerband or not and what the consequences for you if you are not or the other guy if you are.

If you want to find out who has the bigger motor, go to the track and take it down the 1/4 mile. Something else I dont think you are grasping is that most (with the exception of those who really know) will look at a Grand Prix and just brush it off until they get smoked by it or it hangs with them. Ive personally hung with a WS6 Firebird not too terribly long after I got my GTP and we pushed 135 down a VERY long straight away. Now, I did not win that, but nor did he walk away from me either. But you dont think he was sitting there thinking how in hades is a friggin family sports coupe is holding its own against a V8 muscle car? I know I dang sure would have been asking that. To this day, whenever I see him around town and I was in the GP he waves at me.

It doesnt matter what motor you have, how much money you put in to it and so on, there is ALWAYS going to be someone out there that has done more, spent more money and occasionally you run across a car that you know dang well you should be able to knock out and yet get your doors rattled.