Around normal roads I'm as quick on a old Monster (70bhp maybe when it runs!) as I am on the 1198, and usually the Monster is as much fun. Don't take it as me saying the Monster is better though - it's just sometimes more fun at real world speeds rather than the straights at Snetterton!
I have about 100bhp and it's enough, but I think I want a bit more than enough just to keep me scared.
When I had a bike with about 90BHP I thought I'd never need more. Then I went to about 130BHP and thought I'd never need more. Now I have 150BHP and 180+BHP. I'll never need more. Until they bring out the 200BHP version and then I'll need that. Sometimes (on private roads) I give it the full beans and still PeterT was pulling away when I had my SF848. Now I've got a bigger dick than him so it's OK. I hate the expression "in the real world" but the reality is I'd enjoy any bike, I've ridden Harleys with way less power and still had fun. I'd happily buzz about on a 125 and play with getting the most from it. I had a Varadero 125 commuter that topped under 70mph but was fun to ride and you had to work it to get some from it. I'll get a Triumph scrambler at some point and look rather fetching in vintage clothing and a labrador bungied to the pillion. It's like women, some bikes are dark secrets you'd happily play with but wouldn't want your ride being seen in public. I need to find a C90 vintage and take it to Box in full leathers.
In my defence, I do biking holidays in the US and needed to look like a Wild Hog. If you're hiring a bike there, the easiest and most common bikes are all Harleys and for touring they fit the bill. Anyway, a lot of people knock HD but once you get in the groove of what the bike is about then it's still the best way to enjoy long days riding around remote parts of the US.
Horsepower and Torque are only 25% of the game. The curve is vitally important if you want to use it comfortably on the road and the track. The weight of the machine makes an immense difference to it's ability to change direction and accelerate, the quality and set up of the suspension will make a huge difference to your ability to get around the wigglys. It's the balance between them all that matters. I have had cars at 500 bhp/tonne and all the power at 6000 rpm (Caterham R500) - mad, undrivable on the road but not much beat it around a track. Cars at 300/tonne with a much more even power curve (R300) - rapid and exciting enough for the road and not much slower than the R500 round the track. A much better car IMHO. Cars at 1.8 tonne making 400 hp (audi RS4) - Like riding a fat bird. Didn't go round a corner without loosing £100 of rubber and wouldn't stop without nuking the ceramic discs. A pig. Porsche 964, 1.4 tonne and 250 hp. Nice, but could do with a bit more if it was going to be classified as exciting. The new one is a 911 Outlaw which will be 1 tonne and 300 hp. I think 300/tonne for a car is about right, with plenty of low down grunt so it is usable on the road. Interesting that on the bikes the figure seems to be between 500bhp/tonne and 750 bhp/tonne. Add rider weight to that which is a big % on a bike and you get to between 350/tonne and 550/tonne. The 999s is about 500/tonne with me on it with properly set up Ohlins. Lots of grunt down low making it very usable on the road. Certainly more than I need for the road, but shit does it feel good!
400 BHP in the UK is adequate - my Land Speed Record Hayabusa had to be turned down from 440 BHP to 400 to set it's record due to traction issues on our short 2.1 mile runways although Jack Frost has built one now at 700 BHP so waiting to be proved wrong :Bucktooth: