You might try a non-WSD version of the same bike or determine what, if anything, can be changed up to make either the 51 or 54 WSD fit. What, precisely, feels too big or too small on the bikes anyway? The reach? It's easy enough to tweak that via the stem.
If you do look at other brands, take a look at their actual specs to see how the geometries compare. The size only tells you so much.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher