paskal explain it nicely i think
rs70 avr is a higher model than the 519 avr
bt which ever package u choose
u would b satisfied wit the sound
bt if u wanna b future proof abit
its btr to take the rs70 package
it supports dts hd n dolby hd
whereas 519 doesnt supports it

im a user of the 519 package
cuz tat time rs70 no more stock
i brought it around half a yr ago
n im gonna change the avr to 919 soon