I bought a very large chest made of teak and mounted a 50" LED TV to the inside of the lid so we could hide the it when it wasn't in use. The lid (with the tv mounted) is about 80 lbs and 24" from hinge to lip. I want something that keeps the lid open at 90 degrees and keeps the lid from slamming when it closes. The best thing I've found are a pair of these Stabilus gas springs but they can only handle 56lbs. Is there a better product for this application?
A commercial grade door closer might do the trick. A door closer can be set with a limit to prevent the door from opening too far, and can close the door once triggered. It gets its power when the user initially opens the door. In your case, you would rig the closer in reverse to assist (close) when you open the lid and resist when closing it. The important thing is that commercial doors are heavy and the closers should be strong enough to offer real assistance in your setup. A good commercial carpenter would be able to assist you on selecting the right style of closer and how to rig it in the cabinet.
I assume you've read the detailed specs on the gas springs, because simply taking the pressure from the website and equating that to the mass won't work. They may still do for damping the closing movement.
Automotive gas springs may have a higher load.
If you want it to hold at 90 degrees you'll need some kind of stop. And the lid will be nearly balanced at this point. So some big rare-earth magnets in the stop may be what you need. You can buy them with a countersunk hole for screw fixing, though I suggest also sinking them into pockets with just enough recessing that they don't hit each other.
I've taken the whole weight of a decent size monitor on quite small magnets.