Daily, think of it this way.
Your head unit gives out full range audio but your speakers are designed to perform in their certain range. Tweet is high range, mids are for mid range and bass is for low range,.. thats all based on frequency (hz) the stereo puts out.
If you block the signal with base blockers to the mids and highs so they can operate in their normal range without fear of them distorting because they are not designed for those signals.
The base blocker filters out the low frequencies. When we were kids, we would use a coil to eliminate the high signal from hitting the subs to let the sub have its sole range of low base.
So, with your head unit, you need to use that amp just for the sub, and turn down the low frequencies in the head unit for the front channel. All you need to do is listen to the speakers with the sub off, then if you under power them you can do damage to them just as over powering them
The best setup is to have a 5 or 8 volt preout from the head unit where you must run a mono amp, and a multi channel amp to get each speaker to shine in its preset design. That will give most clarity and you will be able to control each speakers thru different amps.
Im not a stereo guy, many others could explain it alot better.
I would just replace the speakers and make sure you dont buy too big of speakers that would be powered by a 200 watt amp, and your head unit is putting out 45 per channel.
In the long run, buy old fosgate stuff, they were underrated and thats what i have in my daily.
HTH
BW