Rusty1234,
Because the Platinum Audio Solo's yield a full range, accurate and musical presentation with high power solid state amps you should be fine with your classic Marantz 500.
Of course, exactly what you will hear depends on each of the different parts of your system, not just the amp.
At one audio store, their finest Solo demo using a solid state amp featured the biggest Aragon amp, an amp of the speaker's time. That Aragon was like your Marantz, built to be a heavyweight champ impressing both sonically and visually.