So i recently replaced 4 of my speakers in my caravan, but i still have the stock headunit. (so the Res radio). I've also installed an amp + sub and wired it into my stock radio.

My 4 speakers are 3-way Kenwood 6x9 in the front
JBL 928 in the rear.

My problem is that they are not connected to an amplifier and that they don't sound better than the speakers that used to be in. Sure they go louder and sound crisper but it is way to high pitch and cracky sounding if that makes sense. When i turn up the volume it hurts to hear it after a while. So i went to Futureshop and asked about replacing the headunit with a single din (i dont want to spend 400$ on a touch screen radio since this car is for my dad) but they told me that even if i tried to splice the wires to get the radio to work (to bypass the whole harness) i might lose out on features on my car. And they were telling me that there are two options a 129.99$ harness that does not include steering wheel controls and a 199.99$ harness which does include it. Can i get some real help? again i have a 2010 3.3L dodge caravan