I purchased an
Ultimate Support Apex AX-48 Pro B (black) when I got 2 boards, and when I decided to add a 3rd board up top, I just bought another base and set of arms.
The AX-48 holds up to
125 pounds -- and there's about 90 on mine and it's very stable.
I do have some weights on the back leg and I use the little adjustable-foot at the lower front because mine is placed on carpet (it slides up/down to ensure the base is level with no rocking on various surfaces). I like it a lot -- it works great, packs up easily into itself -- and I even added the top which allows a mic boom to be attached (I use that with a quick-detach music stand when I'm learning new stuff).
Top-to-bottom 1st image:
Yamaha MODX6, Crumar Mojo 61 (but now there's a Hammond SK Pro 73 instead) and a Roland RD-88.
Good luck.
Old No7
ps: See 2nd image below. If those are "good enough" for Rick Wakeman (saw him on opening night of his U.S. tour last fall), that's a pretty darn good endorsement!