Cool.. I have a stack of 3 1x10's running from an Aguilar AG amp (500w) ... So 165w to each cab... More than I will ever need..!!
I also have a 2x8 cab running from an Elf, which is different sounding again...
As I understand it, your 500w amp will supply an equal amount of 'juice' to each cabinet.. So 250w each. Your cabs are rated to 300w each so I don't think you need to worry
So here's a thing... Sinatra...?
Considered by many (and arguable) to not necessarily have been a great singer.. but what he did have was an astonishing voice.
The two are quite different...