SD, welcome. If you do get the Sony receiver, disregard the 4ohm setting and leave it at 8ohms, regardless of the impedance of the speakers that you're using. These switches or menu settings are a required safety precaution to help prevent overheating. They do this by reducing the maximum voltage capacity, which also reduces the maximum current and power available, because of Ohm's Law. So, it limits overheating but also limits maximum performance and shouldn't be used.
That receiver and others can drive 4ohm rated speakers such as M80s; the question is how loud and how long. In many cases, unless operated at very high sound levels with materials having a very wide dynamic range, there would never be a problem.
