Sorry that "investment" didn't turn out well for you, Bob. Not sure what point of the eighties you bought your set, but in 1980 the silver price nearly hit $50 per troy ounce, only to fall back to $20 a couple months later. If we just take the melt value of a silver coin and silver near $16 today, a silver coin bought in 1980 most surely means you took a loss. That said, remember that only five of your 32 coins are silver dollars. The rest are metal alloys and have no intrinsic value beyond the $1 face value and some collector's value.
There is a huge difference between investing in bullion and common numismatic coins vs rare coins. Silver & gold bullion and common, high mintage numismatic coin series from the past tend to hold low collectible value, meaning you are pretty much only exposed to changes in the spot price. Rare coins however, have a numismatic collectible value that goes way beyond what a coin is worth in its weight of gold or silver. This is where things can get dangerous for the "investor", since rare coins are like works of art: they're only worth what people are willing to pay for them. We have an excellent article about that here:
http://www.coinvalues.com/blog/is-it-wise-to-invest-in-rare-coins.
Eisenhower dollars are quite common today and bought and sold in the thousands each day all over the country. If you are not in a rush to sell, you could just sit on them until the silver price goes up (many believe that the silver price is being artificially suppressed). At that point your silver Eisenhower Dollars will go up in value, though the rest of the set will likely never be worth much more than face value.
It is also probable that an AMEX offer was probably not the best place to invest in an Eisenhower Dollar set at the time. Thanks for your question and good luck.