This rig requires an external relay when used with a linear amplifier. Switching an amplifier directly from the transmit/receiver contacts in the radio can damage the radio. If you want to build one yourself, check out this circuit: http://www.k6xx.com/radio/ic706amp.pdf . This homebrew circuit uses a transistor interface and will fail if connected to a Heath SB220/201 or similar models having higher voltages than +40VDC and may cause damage to the radio T/R switching circuit and will also not switch an AC based amp relay. So, be sure to measure the amplifier relay voltage prior to using this circuit.
The Icom IC-706 is easily computer controlled. I use mine with N1MM for contest logging and DxLab for every day logging. However, to get the 706 to function I had to set the IC-706 CI-V address in menu 34 to 48H. Since I like to travel light, I don’t use a CIV with the 706. Instead, I use a 9 pin din to mini-phone plug cable with an integrated level converter. You can buy these on EBay but be careful that the seller has some good feedback. I once purchased one that didn't work.
The 706 has the same issues with dynamic mikes as does the 781. See the 781 notes above. I use an inexpensive boom headset made for computers with my 706. These computer headsets have condenser elements in them. That's what you need to modulate this rig properly.