Definitely look into Orion speakers.
Clarion head units sound great as well. I have both and I don't even use an amp. The head unit pushes out like 22Watts RMS on each channel and it's crystal clear at all volumes.
I also got a self-amplified 10 inch sub w/ enclosure just to fill in the low freqs.
Really, that's a great setup if you just want it to sound good in your car, and not outside of it.
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