This product was mentioned in
with an average of
yep me and my dad built the arcade cab, a PC runs it...the bottom 3 screens are 24in 1080P the top 3 are 19in 900P, they are supported by this Note I have a different desk and keyboard now, but everything else is pretty much the same.
If you know exactly how you want your setup to be, plus any flexibility in case you change your mind, then perhaps making your own wouldn't be too bad if you're up to the challenge and have a guide to reference to. I'm dubious towards mounts that have to clamp down to a table since various desks do not have the space in the back to allow this. A free-to-move-about stand would have to have a heavy and wide base. I don't know of any like this except for a six-monitor stand my supervisor has (which actually allows you to add/remove the second row). It works really well and would easily meet your needs, the only implications being that the row bar would stick out beyond your monitors.
Consider this. My brother has it, and it can support a ton of weight and not tip at all. Supports up to 6 monitors and he currently has 4 on them.
Or, did you mean the motorized desk cannot support that weight?
Cost wise. The stands I found for the 3 down 1 up were $400+ for that type of stand. I got the 6 monitor stand for $120 on amazon.
I did this build 2 years ago and have 2x 680's running 3 monitors each