This is a common one for us, but it depends on requirements.
for example, if you only have a few needs for it then you could use If (im guessing from your syntax your on revo)
[[If &subject=`[[*id]]` &operator=`EQ` &operand=`6` &then=`[[$salonSide23]]` &else=`[[&standardSidebar]]`
however if you need to have different chunks on each individual page - so lots of different chunks per page you might be better with a TV selector for setting a chunk on a page
see this:
http://wiki.modxcms.com/index.php/Create_TV-Based_Chunks - but make sure you get the revolution version of the snippet at the bottom.
admittedly the second version needs you to select it for every page but it gives much more flexibility unless you plan on writing If statements for every ID value.
edit:
you could also use the If statments to set the sidebar based on parent if the subpages to a parent need to have the same chunk
[[If &subject=`[[*parent]]` &operator=`EQ` &operand=`6` &then=`[[$salonSide23]]` &else=`[[&standardSidebar]]`
you would need to set the parent id of 6 with the first call however if you neededit to display on the parent page though - i would use AndIf in that instance (
https://forums.modx.com/thread/?thread=63762&i=1)