Can't comment on a music stand/tablet holder, as I don't use either of those live. If I need my iPad for anything, it just sits on the right-hand side of my MODX7.
As far as 2-tier stands, I have a couple that I use: an OnStage double-tier Z stand, and a 2-tier Stay Tower.
Sadly, Stay stands no longer have a US distributor. They will ship to the US from South America, but the shipping costs could be a lot higher than what the stand is worth.
I've had the OnStage Z stand for almost 15 years. It's definitely showing its age from being gigged a lot, and yes, it consists of a million parts, kind of like a piece of Ikea furniture. I just tear it down in two parts: Main stand stays together (two sides and crossbar), and the whole 2nd tier assembly. I will say, that it's the most solid-built stand I own. No side-to-side wobble at all, even with a 95-lb Roland RD-1000 sitting on top of it (not that I gig my RD-1000, mind you.)