New speakers don't sound good

YzGyz

From experience, any decant after market audio system with amp (even if junk) sounds better than stock. I suspect a crappy install. Another thing to consider is that not all speaker are meant for a specific sound. You have to shop specific speaker for specific type of sound. This "may" explain why certain songs sound good, bad, crap in your set up. Only advice I have at this time is to let the shop finish the install since you have already paid them. It is a very small chance that you can get you money back now. If Your system is still not up to par after they fiddle with it, find a friendly local that knows a thing or two and have him/her take a look.