Hello Haryn, Welcome to the board.The 16 ohm speakers were designed for Tube Amps really when solid state started they then switched to 8 ohm speaker loads.As for your X-overs yes the tar-filled X-over box sounds like Heathkit but the drivers don't Heathkits were painted Gray.But it sounds like one pair is a Heathkit.The behringer crossover you speak of(Active) are for bi-amping or you can bi-amp with them.Which you can't do with the passives as you have.You are more familiar than you realize.After 3 posts you can post pics do you have pictures that would go along way of helping people here help you.Are you interested in keeping them stock original or upgrading them because the N800-K isn't a very good X-over the Heathkits are better but are a PIA with all the tar in them to repair.Foam would not be a good dampening material for the horns a better solution would be to buy some automotive undercoating that comes in a can that you could spray on the outside part of the horns very fast and quick application just keep away from the mounting flanges....

It's a shame that you didn't go to GPA first they are the only place for replacement parts for Altec Lansing speakers,components,etc..