I would stay away from something like what you found at tiger Direct. Your store is sizable and you should do it the right way. I am going to assume your store has a drop ceiling. Focus your research at in-ceiling speakers and you'll want to do a 70 volt system. With a 70 volt speaker system you can daisy chain the speakers together so wire running is easy, going in-ceiling will give you good coverage without having to install a lot of speakers, and they are unobtrusive. Then you'll want to look for a 70 volt amplifier. They have 70 volt amplifiers that have volume control, and multiple inputs so you can hook up your computer and anything else. Sonos is really popular for stores like yours, it's basically FREE internet radio that you can control from your Android or I phone.
For the amplifier I think that 120 watts would be sufficient and you'll want to tap the speakers at anywhere from 2-6 watts. Just be careful you don't exceed the amplifier rating. For example: you have 8 speakers and you tap them at 4 watts. Well that's 32 watts. Well within the 120 watt limit of your amplifier. Good luck!