Seriously though, wait for CowboyNQ to chime in on this.
Haha..thanks Gary, chiming in as predicted!
If you look at my avatar you can actually see my set up, exactly as Gary (happyrat1) described.
My question is, does it make sense to buy a three tiered stand for all three instruments? Or is should I use a double stand for the two I'll use the most and a single stand for the one I'll use the least.
To be frank, it's really what suits you. I'll explain what I do and why, but I guess there's no right or wrong with these things.
I have a weighted 88 keyboard on the bottom tier of a K&M 18880, and a lightweight 61 key synth/workstation/rompler/whatever you want to call it on the top tier. These face across stage pointing towards the rest of the band. This suits me because our show is very technical and the drummer and I interact constantly with little eyebrow raises and head nods, etc.
My third keyboard is a VA synth and points towards the audience. The reason I use three 'boards is twofold:
1. I run a multitude of mid-song patch changes, and I need the extra keyboard real estate to make it all work.
2. In this particular band (Pink Floyd tribute) I really want those lush VA sounds for certain leads - my other keyboards can't quite pack the punch my VA can.
The reason I configure in the L-Shape rather than a three tier stand is as follows:
1. I like to stand up when I play. I'm a little worried about stand stability on a 3-tier rig with such a high centre of gravity. The K&M 18880 does have a three-tier option, and it's a very sturdy stand, so I'm not worried about it spontaneously collapsing. However you'd be amazed at the mayhem that goes on during set up and tear down. All it would take would be a rushing sound tech or a gesticulating bass player to accidentally knock into the top tier and ...JENGA!
2. As mentioned I like to face the drummer, but I do also like to turn towards the audience too from time to time. Having the "L" allows me to do it without looking cheesy, like I'm mugging for them.
3. I often play more than one keyboard simultaneously, and I don't like my hands being at such different heights. Reaching across to cover the "L" doesn't bother me nearly as much.
4. More real estate for my various pedals.
I should add that this band only every plays on large theatre stages, so the extra room taken up by the "L" is never an issue. I also play in a pub covers act, but I only use two (or sometimes one) keyboards for that.
Hope that helps - good luck with your setup!