We have had a Kings Down #3 for about 18 months, and it is too firm for me and hurts my back.  I have been considering buying a new mattress, which of course means I am throwing away the $2000 paid for the Kings Down, but good sleep is priceless; right?  Anyway, I've noticed some comments on the forum about some people buying latex toppers and achieving more comfort.  Is this a good idea?  Or just a delay of getting the comfortable mattress I'm longing for?  Also, any thoughts on the latex mattresses for someone who likes a softer feel?

A too firm mattress is always better than a too soft one. Unless you're happy to throw away $2000 you're in the perfect position to customize your comfort level by adding a latex or memory foam topper. You may have to tweak things before you get it just right. I would start with a 2" topper of soft latex--20-23 ILD or 4lb MF. You can always add another inch if you want it a little plusher, or try combining different kinds of foams to achieve the ideal result. Some people have added a plush mattress pad like the Costco Cuddle Bed over that to make things even more cushy. Try to buy somewhere you can return the topper if it doesn't suit you. You absolutely CAN make a hard bed wonderfully comfy with the right toppers. And it's much more versatile than buying a new mattress that turns out to be too soft. There's nothing you can do about that.