My $180 solution is much nicer and doesn't require two people to lift.

http://www.leevalley.com/en/hardware/page.aspx?c=&p=4057...

Ignore the text about a maximum of 20lb. When you get it, it's actually a MINIMUM of 20 lbs required. 20lbs is the balance point: if you have less than that, it stays permanently up. But if you have less than 20lbs you can take out one of the springs. Of course, most woodworkers using it for it's intended purpose use 20lbs of hardwood, but I use a jerry rig that's much lighter. Then I added a 30lb 30" monitor, and it works great. The springs lift 20lbs, so you only have to put in 10lbs of effort to lift 30 lbs.

I'd worry about adding a lot of heavy weight to the front of it where there is more leverage, but I wouldn't hesitate to add another 50lbs to the back. This thing is solid.

Of course, it's a fixed travel distance. But if your monitor also has a little bit of height adjustment as well, it'll work perfectly.