Need some suggestions for setting up speakers in an 80' x 88' retail store space...

Need some suggestions for setting up speakers in an 80' x 88' retail store space w/ 15'-16' high ceilings. We had 4 junk speakers positioned roughly 10'-12' feet out from each corner. One hasn't worked for years and the others started sounding muffled or blown here not to long ago. All 4 speakers were looped together, leaving just one pair of speaker wires actually coming down to a receiver. This was done before we bought the store. So, w/ out spending a fortune, what are some suggestions? Since the store is so large, can we have more that 4? Can we keep the speakers looped or in a "series" or would it be better to run individual wires? I am obviously a novice at this, so any "retail store speakers for dummies" advice would be greatly welcomed. Thanks!