If really worried about power an avr with a full set of pre-outs allows amplification flexibility, all of these have such. Marantz and Denon are from the same company and I'd simply choose which model depending on the feature set you want at the best price you can, they will be very similar to each other in terms of general features, altho in terms of Audyssey, the 70s only has MultEQ, the lowest version of Audyssey, the others have the highest, XT32). If you overdrive an amp yes damage to speakers can occur, but you'll likely get audible warnings first (depending perhaps on state of mind)....volume control is your safety feature in that regard. B&W is the usual abbreviation, especially as B&O would be Bang & Olufson.
This is a nice site to help compare different avrs
https://www.zkelectronics.com/receivers/
How loud do you listen? You might play around with this to help determine amp needs
http://www.hometheaterengineering.com/splcalculator.html
