1. Factory 6.5s are garbage, there’s no world in which the two are comparable other than the size.
2. Your HU puts out 45w RMS
3. Your diamond 6.5s are rated for 200W rms and will tolerate 300 without blinking
4. Your HU will send a full spectrum of sound to the speaker. 20hz to 20khz. Your speakers will effectively play between 110hz and 10khz. The speakers you have need, not want, a DSP to bandpass the desired frequency. Same goes for your horns. Without looking them up, I’d bet they play from 3500hz to 20k. If you send a full sound spectrum to a horn you will ruin them, even if it’s only 45w.