Personally I never used the volumetric feature on my EM6910, I prefer to go by the pour and stop manually. *Volumetric is certainly handy if youre making large amounts of coffee and frees you up to steam milk.
Optimal conditions for pouring will vary depending on bean type, age of beans, room temperature, humidity, etc. *Using a programmed volume will not be optimal for that reason. You could always pour manually when making 1-2 then revert to auto if entertaining for large numbers.
I believe for your requirements any HX machine should be able to handle with those numbers pretty easily.
The Bezerras come very highly recommended... you may want to look at the BZ07DE