Your 600 is going to be 110 hp at the wheel. The RC8 is going to be 150. A CBR1000rr is closer to 160. Any liter bike is going to be 40 or 50% more power in a chassis maybe a few kg heavier.
The thing about riding a liter bike is that you can be lazy and leave it in a higher gear because they will still pull very hard from lower rpm compared to your 600 (the v-twin probably more so than an inline4). And that is probably what you will do for a long time. Some people will always ride them like this... they will be no faster than a guy on a 600 in the mountains, but they wont have to work as hard. However, ride a liter bike up in the 10,000+ rpm range and your mind will be blown. Your 600 will seem like a slug. [enter all the typical warnings here about wheelspin, wheelies and acceleration quick enough to catch you out]. The good thing about the rc8, s1000rr and similar bikes is their electronics... traction control, abs, anti wheelie etc.
So... do you need to thrash it? An RC8/S1000RR is effectively a race bike. You cant thrash it... it always wants more. I think it unlikely you will see the bikes limits (I dont know you, just stating the odds). Just dont f something up while trying to get there.
And my personal advice for any decent sportsbike owner... never skimp on tyres. Buy the best you can afford.
PS. I keep re-reading the above because I know someone is going to say that a 600 will still be quicker in the mountains for half the price. The thing is this all comes down to the rider and so its mostly based on personal opinion. A 600 is probably easier to ride because of the few kg's less, slightly more nimble chassis and no fear of excess power. A liter is much more likely to scare you.
If you keep staring at an RC8 in the shop window, I can guarantee that you would not be disappointed riding it. If your entering a 1000cc racing class at the track, I'd get the S1000RR. If you want to ensure you beat all your mates from the lights, buy the S1000RR. The RC8 will still feel like sex every time you climb aboard.
