Hi. As others have said - you'll be fine.
The RS-42 II are rated for 75W RMS / 300W Peak. They are also rated at 93 dB @ 2.83V / 1m (which is about equivalent to 1W / 1m for those speakers).
Here's a
handy website for you to calculate sound levels (first one that I found using Google - I'm sure that there are more).
Assuming the calculations on that site are right - at 75W, assuming that you are about 6.5 feet away from those speakers, the sound level will be about 109 dB. That's loud. Really loud. You won't be listening to that for hours on end, but that's what the speakers are rated for. 300 W peaks would be about 115 dB.
I think that I got that right, but I know that someone will correct me if I didn't.