Just installed a pair of infinity reference 6002si in my 2000 civic. installion was easy enough, but the speakers sound worse than my stock ones, they're really high... I'm running them on my stock cd player. I'm guessing they don't supply enough output???? I guess i gotta get a new HU then? So expensive.
Not nearly enough output. those speakers aren't the best for lower midrange and midbass anyway. You'll really need an external amp to get full potential out of them, at least 50W RMS, an aftermarket head unit won't show a lot of benefit as far as power, it may allow you to cut the higher freqs via an equalizer, but the speakers will still be drastically underpowered.