If your modern audio equipment has a ‘line out’ signal level, then this can be fed directly to the ‘Aux’ input of the amplifier. You might need a converter lead to change the connection type - e.g. 3.5mm stereo jack to twin phono plugs.
If no discrete audio out connection is available on the modern audio equipment – you might find a cable connector/splitter that makes such a connection available. The best place to search for such a cable is on ebay.
Would an amplifier make much difference to the sound of todays audio devices , given that the amplifier was to boost what was a low level signal from the turntable ?
It could make the sound "different", depending on the quality of the modern stuff with which you compare it.
However, the greatest difference in sound quality is likely to be from the quality (or lack of it!) of the loudspeakers or headphones.