Let's put it this way--RMS is only a measure of how many watts the speakers can tolerate continuously without blowing up, and has nothing to do with quality (distortion) or loudness (efficiency).
Rather infamously, Bose speakers have a surprisingly high RMS rating for their driver size because excess power is shunted to an incandescent light bulb inside the box. Does this extra power handling help you in any way? It certainly helps Bose because it reduces RMAs by making their speakers really resistant to misuse.
Most people are going to listen to non-sub speakers at around 1 watt, as even relatively inefficient 85dB/w small speakers at 1w unsurprisingly are the OSHA maximum safe volume of 85dB at 1 meter. It takes more than 4w to push those to over 90dB. If on the other hand you buy very sensitive 97dB/w large floorstanding speakers, you will also tend to listen to them around 1w, because those tend to be placed further away and there is a 12dB drop by 4 meters, also resulting in 85dB. So the vast majority of that 40 or 48w should be directed to the sub