Conclusion: The Apline SPS-510 speakers fit perfectly in a small space, were easy to install and sounded better rounded that the Kicker's that they replaced. For a small speaker they put out a big sound that perfectly compliments my Alpine head unit, I was especially pleased with the full mids & crisp highs. My only complaint is that Alpine should have used a metal frame, one of the plastic mounting spikes cracked when I was installing it.
Summary: Speakers sound fine, however, the casing is not reliable. Unlike most speakers that have a metal frame, mainly for attachment, these are plastic. When i recieved from seller, part was broken, speaker still works but when these go out i will not be purchasing another set.
Conclusion: Bought 2 for aftermarket speakers on my Jeep Cherokee, very pleased. Very clear sounding speakers, great treble and good enough mids. Fair bass improvement over the stock 5-1/4" speakers. Got mine when they were in the 50 dollar range however. Might recommend an amp if your thinking about going crazy with the loudness. Overall great upgrade for stock 5-1/4" speakers.