How would you upgrade my entry level system?

... and I'm assuming you have fully broken in your equipment - that means 300+ hours of continuous play (I usually do double that): most never really break their equipment in, consequently never really knowing how good their equipment really is...

... FIRST MAKE YOUR OWN SPEAKER CABLES: twist lengths of 14g Solid Core Copper wire from an electrical supply place (I paid $0.20/lf), install with bare wires and play for 300 hours. You may find you have rebirthed your system with enough improvement that you'll buy more music and have an increase in enjoyment instead of more neurosis...