op
i am with @mesch - don’t spend too much on cables, improve your room, your components
your speaker cables and power cable are just fine, totally in line with the quality of your system... as @soix says, if you play with cables to see if you hear a positive change, try a nicer set of interconnects - buy used, under a $150 a pair, read up on the sonic traits of various brands, and adjust according to where sonically you want to take your system (more open treble? smooth out sibilance? more body to voices? and so on...)
as for @ted_denney saying "A better question, what system would not benefit from cable upgrades?"
my answer would be, a relatively nice sounding budget system with quality bottlenecks in room matching and one or more components in the chain - not to say cables wouldn’t benefit, but it is a matter of priority of what to improve first, for greatest sonic benefit