Ugrading Fronts

I am a newbie and need help. My system consists of Dennon AVR 886 (100wps/5) Bose 4001 (401 equilivent Sam's Club) Fronts, Paradigm Atom rears, Signet Center [Out of business but higher-end stuff], and Paradigm 10" Sub driven by 250/RMS NAD Amp. My room is 11/17 and carpeted.

For home theatre use this mess actually works pretty well. The issue is music. In 2 channel stereo the Bose speakers sound lifeless and the mid-highs sound harsh. In the 5ch stereo the system comes to life with the Atoms and center helping things out. Obviously, the weak link is the Bose. I am looking for a used pair of fronts with Mid's and Highs that will work well with my sub. I would still use them or home theatre. I really don't want to spend more than $500.00. Your input would be appreciated.