Some of the production runs of the Marantz 240 and 250 power amps were quite nice. Of the vintage-correct speakers, Large Advent, Dynaco A50, Dynaco A35 and Dynaco A25 mate well with these Marantz transistor amps, taking the edge off the top end and making good use of the amp's high bass resolution. If your 250 is a particularly smooth one, it can also drive Dahlquist DQ10 nicely, and I know of a few such systems in use still today.
Phil
Phil