Peter,
Maybe you need two small powered speakers...I never thought the 3k(or S900) sounded it's best when put through a mono amp, especially the piano sound.

I use two 60 watt powered monitors that weigh less the 30 lbs each...Yamaha MS-60S is the model...discontinued but sometimes you find them for sale, but not often as people seem to keep them...mine are over 15 years old.

The Traynor K4 is really good but a tad heavy.

The Roland CM30 powered speakers come highly recommended from several member on this forum...the price is good.

Good luck.

Ian