Dennis,
I have had my Kurzweil K2600X ( Heavy) AND a Korg PA2XPRO on the On Stage Stands model with 2 tiers, no problem...solid as a rock.

The legs are long enough that that typical rock forward and back is minimizd. (like on some X stands)

It is not quite as heavily built as the Quick Lock model I have, but good enough I believe.

Lee