I know you don't have the router any more and it's being replaced, but the only way to free it at this point is to lay it on the side with the collet end hanging off the end of a work bench. Put your wrench on the collet so the wrench is sticking out horizontally. If you have a metal sleeve that will fit over the wrench handle to extend it a foot or so, slip that on, as the next part is the fun part. Hold the router against the table very tightly with one hand, and with the other take the largest hammer you can wield and smack the handle of the wrench (or the extension) as hard as you can, downward. It's critical you hit it hard and fast. Now keep in mind that the wrench and handle are going to fly off and down in to the ground when you do this, so all kinds of noise and banging around will ensue. Keep doing this until the collet loosens up. Sometimes you have to hit it a couple dozen times. The key is to whack it really hard. Not pretty, but it will almost always work. Using a lubricating or penetrating oil will facilitate the job.
I suppose there may be other ways to do it, but I've seen at least a few hundred collets, lawnmower blades, drill chucks and the like come free using this method when all else failed. You do end up with a banged up wrench handle though.