Yeah, those speakers are being horribly underpowered. Headunits are NOT equipped with amplifiers anywhere near powerful enough to drive component speakers. Keep in mind your 45w Alpine is probably only putting out 22w RMS, if that. Those speakers want at least 100w RMS.
You need an external amplifier. Period.
Here are the specs for your speakers: http://www.infinitysystems.com/car/p...=US&Region=USA