Two different series of avr, the S series is in a slightly lower range than the X series from what I've observed but haven't really dug into it, sorry; the numbers do get bigger as you go up the Denon lines, but don't really match up to any sort of comparisons based on the model number. I have a Denon 4520 from a different model line than either. The wattage makes less than 1dB difference in spl (sound pressure level); it takes a doubling of power to gain merely 3dB (which is a slight increase in volume, less than 1dB is very hard to perceive). Are your speakers particularly low impedance? That would be a greater concern in an avr.
You might check out the official threads at avsforum.com for the
910 and
1300, they're very detailed and helpful and you can ask owners of either specific questions, too. They're from different year runs and may be quite similar; one thing I think I've read is the 1300 gets the new Denon android control app for Audyssey; the 1300 has a higher version of Audyssey is one thing I noted from glancing at those threads...
You really should familiarize yourself with the features....or tell us what you've got and what you want to do....
