looks like you will need these to soft close

http://www.rockler.com/product.cfm?page=410&rrt=1

125lb's each

 

The Rockler calculator is very conservative; in that, it will over-recommend the number of hinges. I recently completed a Cherry Blanket Chest - the lid had an 'effective' weight of 180 lbs - Rockler recommended 3×60; they had two in-stock, which I used - the lid works perfectly with 2×60.

Appreciate that the 60 in-lb rating will tax the holding strength of the hinge screws - the wood and the screws can handle only so much, regardless of the hinges' mechanical capabilities. If higher-capacity hinges are available, I'm not sure the wood could handle the torque.

On mine, see pictures below, I placed a spacer between the hinge and top - the spacer is glued to the top - spreading the load, with the hinge connected to the spacer: if the spacer is stripped, it can be replace.

My recommendation is to use something less than the 6 (probably 4 or 5, which should look fine); if you need more; we'll you'll need more, and can put them on later - I appreciate the layout issues with this, as you would want to equally space 6 or 4, and do not want to make it look like an add-on, or after-thought
MJCD

 

Follow-up:

On the Rockler site, please read all of the user comments - several noted that the screws supplied with the hinges were, in their view, undersized for the task; also, that some of the screws snapped during installation because of the twisting force during installation. I pre-drilled the holes and used slightly larger stainless steel screws - my choice, for your consideration.

I hope this helps.

 

Patron's solution looks like the better choice - I think it will be a) less demanding on the wood contacts; 2) handle your requirements in a less obtrusive and expensive manner.

I would check the user comments, though; these are usually very knowledgeable craftsman.
MJCD

 

The lid on the toy box I just finished was made out of white pine so it wasn't very heavy. I used a piano hinge and two of the lightweight lid protectors sold by Rockler. It won't close on it's own, thus protecting little fingers. You have to shut it.

http://lumberjocks.com/projects/72425

 

Brusso makes an awesome hinge for a chest like this. You bury it in the top edge of the side (at the back). Pricey but beautiful solid brass.

 

I used the "Lid Supports" that @Stringer mentions, however with my Ash Blanket Chest it took three of them to handle the weight. Maybe a combination of these and the torsion hinges might be an acceptable answer.

 

Wow, thanks everyone for all the suggestions. Great feedback!