My dream would be a 264 Win Mag. You can even use your old 300 brass to make 264 brass. The 264 will out perform the 6.5WSM for the same barrel length.

There has been a history of not getting the accuracy from the overbored 6.5's like the 264 Win Mag and 6.5WSM. I would personally consider the 6.5-06 as a re-barrel as well as getting better barrel life.
That is a pretty big cartridge for a poodle or paper slayer. If that is the extent of the guns and want high volume use you might consider something that even kinder on barrels like the 260 Remington.

Curious to hear other peoples opinions.