Hi all,
Z stands are solid, just not real easy to deal with and transport: better for semi-permanent home or studio setups, I'd say. I bought one and returned it, as it didn't go low enough for my needs.
Agreed about the Ultimate IQ 3000: rock-solid, wobble-free with two tiers. Top-notch customer service from Ultimate (they sent me a replacement part for a 10 yr. old, second-hand broken stand for free). This is one beefy stand; look at their website for the second tier option.
I have the Quiklok 642: has two tiers, but differs from the 641 in that the second tier is NOT height-adjustable (i wish I realized that before I bought it, as the price difference between the two is like $15, whereas the cost for the conversion kit is $50!! Quite a ripoff, Quiklok....). I've since adapted to the fixed height, but...
I have a Roland A-90EX (60 lbs) and Roland A-70Ex (40 lbs) on it, and the Quiklok works fine in my home studio: I'm the only staggering drunk allowed in my home and I, even in a drunken stupor, know not to fall on the MIDI rig.
Chris