Ok, I've calculated many different ways to do this and most of them will cause you to ruin your amplifier. If i'm not mistaken, your amplifer is 8 ohm unbrigded. So with your way of doing it the two 4ohm pairs would be 2 ohms hooked into the 8ohm spot in parallel, or 8 ohms in series (which would sound weak). The other side, the 2 8ohm speakers would be 3 ohms in parallel or 16 ohms in series. Both of these would be bad, the parallel connections will make your amp unstable and possibly burn out or catch fire. The series way will will cause your volume to be so low it would suck. Never go under the ohms that your amp suggest. It will break over time if not right away. Going over will cause volume issue because of a complete lack of power. This is what I'm suggesting but first let me tell you how to figure this out yourself. This is the resistance formula. R1XR2/R1+R2. With this formula the closet I can get you is 5 ohms. First let me say this, it would be one channel not 2 (because it has to be bridged to get 4ohms. If you hook the two 4ohm speakers in parallel [2ohms] (red to red and black to black) and then hook your 8 ohm speakers in parallel [3 ohms] and then connect the two in series (red to black in the middle and the red and black thats not used to the amp) you'll get 5 ohms total after all the connecting. This will be safe however, just to make sure get a meter if you have one and check the final ohms. Also, turn the amplifier down just to make sure you don't mess it up if something is wrong. Gradually give it volume and if something is wrong it should go into protect mode. Good luck and let me know if you have any other questions.