<i><b>The reason I asked was becasue I have read the with lower OHM's you should add more O/P Transistors.</i></b>
That's not a stability issue, it's a current/thermal issue. As you reduce the load impedance for a given output voltage, you draw more current which means more power which means more heat, all else being equal.
A given transistor can only handle so much current. Paralleling multiple output devices spreads the total output current across multiple devices, reducing the amount of current any single device has to carry.
But it's not simply a matter of adding output devices. If you're going to be driving significantly lower impedance loads than the original design was intended, you're going to have to dissipate significantly more heat which means that in addition to adding more output devices, you're going to have to increase the amount of heatsinking.
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