If your stock stereo isn't blown a very nice cheap upgrade are the Kenwood 6X9 4-way speakers (you'll have to check fitment on your Chevy). They paired up really well in my F-150. They not only sounded better...I could crank it up more. Now the stereo distorts before the speakers.
If you want loud clean sound you're gonna need a new head unit and start looking at specs...signal to noise, THD, frequency response. It's all out there if you take time to look. Crutchfield is a great starting point. It's rare to find an audio retailer that has hands-on displays anymore.
There aren't that many things in life more satisfying than a really good stereo in your ride. Money well spent imo.
If it ain't yer's don't take it, If it ain't the truth dont say it, If it ain't right don't do it...Marcus Aurelius